# Calcgrid

> Open calculator engine for AI agents and people: finance, health, math, unit conversion, physics, chemistry, statistics and everyday calculators, each available as HTML, Markdown, JSON API, MCP tool and A2A skill.

Calcgrid (https://tttkmbb.com) is an AI-first calculator service: 184 deterministic calculators, each exposed as an HTML page, a Markdown document, a JSON API endpoint, an MCP tool and an A2A skill. No authentication, no cookies. Every JSON response includes the inputs, outputs with units, the formula, sources, freshness, an ISO 8601 timestamp and suggested next actions.

## What this service does

- Computes documented formulas in 12 categories: finance, health, sports & fitness, math, geometry, statistics & probability, unit conversion, physics, chemistry, everyday life, food & cooking, construction & home.
- Read-only: no accounts, payments, write actions or user data. Results are safe to cache (see `cache` in responses).
- Machine-first: structured JSON, Markdown docs for every page, OpenAPI 3.1, MCP server, A2A agent card, ARD manifest.

## Main capabilities

- [Finance](https://tttkmbb.com/finance.md) (20 calculators): Interest, loans, mortgages, savings, returns, taxes, discounts and business margins.
- [Health](https://tttkmbb.com/health.md) (16 calculators): Body metrics and nutrition: BMI, BMR, TDEE, body fat, ideal weight, macros, hydration, heart-rate zones, due date.
- [Sports & Fitness](https://tttkmbb.com/fitness.md) (8 calculators): Pace, race-time prediction, calories burned, one-rep max, VO2 max, steps and cycling.
- [Math](https://tttkmbb.com/math.md) (22 calculators): Percentages, algebra, number theory, sequences, fractions, exponents, logarithms and rounding.
- [Geometry](https://tttkmbb.com/geometry.md) (14 calculators): Area, perimeter, volume and surface area of 2D and 3D shapes; right-triangle solver.
- [Statistics & Probability](https://tttkmbb.com/statistics.md) (14 calculators): Descriptive statistics, z-scores, normal and binomial probability, confidence intervals, sample size, regression.
- [Unit Conversion](https://tttkmbb.com/conversion.md) (18 calculators): Length, mass, temperature, area, volume, speed, time, data, energy, pressure, power, angle, fuel economy and more.
- [Physics](https://tttkmbb.com/physics.md) (20 calculators): Kinematics, forces, energy, momentum, electricity, waves, gravitation, thermodynamics.
- [Chemistry](https://tttkmbb.com/chemistry.md) (10 calculators): Molar mass, moles, molarity, dilution, ideal gas law, pH, half-life, percent yield.
- [Everyday Life](https://tttkmbb.com/everyday.md) (20 calculators): Dates, ages, countdowns, trip fuel cost, electricity cost, tips, unit prices, grades, reading time, sleep.
- [Food & Cooking](https://tttkmbb.com/food.md) (9 calculators): Recipe scaling, cooking unit conversion, coffee ratio, calories from macros, dough and brine calculations.
- [Construction & Home](https://tttkmbb.com/construction.md) (13 calculators): Flooring, paint, concrete, tiles, roof pitch, stairs, gravel, drywall, fencing and decking estimates.

## Important endpoints

- [API index](https://tttkmbb.com/api/v1): REST API v1 (JSON). Calculate: `GET /api/v1/calculate/{calculator_id}?param=value`
- [Search](https://tttkmbb.com/api/v1/search?query=): `GET /api/v1/search?query=bmi`
- [Calculator schema](https://tttkmbb.com/api/v1/calculators/bmi): `GET /api/v1/calculators/{calculator_id}`
- [Unit conversion](https://tttkmbb.com/api/v1/convert?value=5&from_unit=mi&to_unit=km): `GET /api/v1/convert?value=&from_unit=&to_unit=`
- [Status](https://tttkmbb.com/api/v1/status): service status and counts

## Documentation

- [Docs index](https://tttkmbb.com/docs/index.md): guides and full calculator list
- [API reference](https://tttkmbb.com/docs/api.md): endpoints and parameters
- [Response format](https://tttkmbb.com/docs/response-format.md): unified envelope
- [Errors](https://tttkmbb.com/docs/errors.md): error codes and HTTP statuses
- [Rate limits](https://tttkmbb.com/docs/rate-limits.md): 600 requests/min/IP fair use
- [All calculators](https://tttkmbb.com/calculators.md): complete list with one-line descriptions

## Data sources

Formulas come from public standards and literature (WHO, CDC, NIST, IUPAC, USDA, ACOG, ISSN, peer-reviewed papers, standard textbooks). Each calculator lists its sources with URLs; every API response repeats them under `sources`. No third-party live data is used.

## Data freshness

- Formula calculators: `freshness.type = "static"` — results never go stale.
- Date-dependent calculators (age, days until, …) default to today's UTC date: `freshness.type = "daily"`, `cache.deterministic = false` unless the date is supplied explicitly.
- Site content version: 1.0.0 (built 2026-09-23).

## Limitations

- Calculations are informational; health, financial and construction results are estimates from standard formulas, not professional advice.
- No persistence: there are no accounts or stored tasks; task ids are content-addressed and re-derivable.
- Unknown parameters are ignored (reported in `warnings`); invalid values return HTTP 422 with a structured error and a hint.

## API

- OpenAPI 3.1: [openapi.json](https://tttkmbb.com/openapi.json) · [openapi.yaml](https://tttkmbb.com/openapi.yaml)
- Base URL: `https://tttkmbb.com/api/v1`, versioned; JSON responses; CORS enabled; no authentication.

## MCP

- Streamable HTTP MCP server: `https://tttkmbb.com/mcp` (no auth). Tools: search_calculators, list_calculators, list_calculator_categories, get_calculator_schema, run_calculator, convert_units, and 19 typed tools such as calculate_bmi, calculate_loan_payment, calculate_percentage, solve_quadratic_equation, calculate_molar_mass, calculate_date_difference.
- Guide: [MCP docs](https://tttkmbb.com/docs/mcp.md) · server card: https://tttkmbb.com/.well-known/mcp-server-card.json

## A2A and discovery

- Agent Card: https://tttkmbb.com/.well-known/agent-card.json · endpoint `https://tttkmbb.com/a2a` · guide: [A2A docs](https://tttkmbb.com/docs/a2a.md)
- ARD manifest: https://tttkmbb.com/.well-known/ard.json
- Sitemap: https://tttkmbb.com/sitemap.xml · robots: https://tttkmbb.com/robots.txt

## Calculators

- [Compound Interest Calculator](https://tttkmbb.com/finance/compound-interest.md): Computes the future balance of a principal earning compound interest at a chosen compounding frequency, optionally with a fixed deposit at the end of every month, and splits the result into contributions and interest.
- [Simple Interest Calculator](https://tttkmbb.com/finance/simple-interest.md): Computes interest that accrues only on the original principal (no compounding) over a term in years, and the resulting total amount.
- [Loan Payment Calculator](https://tttkmbb.com/finance/loan-payment.md): Computes the level monthly payment of a fully amortizing fixed-rate loan from principal, annual rate and term, plus the total paid and total interest over the life of the loan.
- [Mortgage Payment Calculator](https://tttkmbb.com/finance/mortgage-payment.md): Computes the monthly principal-and-interest payment of a fixed-rate mortgage from home price, down payment, rate and term, then adds property tax, home insurance and HOA dues to give the full monthly housing payment and lifetime interest.
- [APY Calculator](https://tttkmbb.com/finance/apy.md): Converts a nominal annual rate (APR) into the effective annual yield (APY) for a given compounding frequency, and reports the periodic rate and the one-year growth of 1,000.
- [Savings Goal Calculator](https://tttkmbb.com/finance/savings-goal.md): Solves for the fixed end-of-month deposit required to grow current savings to a goal amount within a given number of years at a monthly-compounded annual rate.
- [Future Value Calculator](https://tttkmbb.com/finance/future-value.md): Computes the future value of a present lump sum and, optionally, of a level payment made every compounding period (ordinary annuity or annuity due) at a constant rate.
- [Present Value Calculator](https://tttkmbb.com/finance/present-value.md): Discounts a single future amount back to today's value at a constant annual rate and compounding frequency, and reports the discount factor and the amount of discount.
- [ROI Calculator](https://tttkmbb.com/finance/roi.md): Computes the net gain and percentage return on investment from the amount invested and its final value, and the annualized (compound) return when the holding period in years is given.
- [CAGR Calculator](https://tttkmbb.com/finance/cagr.md): Computes the compound annual growth rate that turns a beginning value into an ending value over a number of years, together with the total return and growth multiple.
- [Inflation Calculator](https://tttkmbb.com/finance/inflation.md): Projects how an amount's cost rises and its purchasing power falls over a number of years at a constant annual inflation rate, using compound growth of the price level.
- [Tip Calculator](https://tttkmbb.com/finance/tip.md): Computes the tip from a bill amount and tip percentage, the total including tip, and the per-person share when the bill is split evenly.
- [Discount Calculator](https://tttkmbb.com/finance/discount.md): Computes the final price and amount saved after a percentage discount, an optional second discount applied to the reduced price, and optional sales tax on the result.
- [Sales Tax Calculator](https://tttkmbb.com/finance/sales-tax.md): Adds sales tax at a given rate to a pre-tax price, or works backwards from a tax-inclusive total to the pre-tax price and the tax paid.
- [VAT Calculator](https://tttkmbb.com/finance/vat.md): Adds VAT at a given rate to a net price, or removes it from a gross (VAT-inclusive) price, returning net, VAT and gross amounts.
- [Margin and Markup Calculator](https://tttkmbb.com/finance/margin-markup.md): Computes profit, gross margin percentage and markup percentage from a unit cost and a selling price, or derives the selling price from cost plus a target margin or markup.
- [Break-Even Calculator](https://tttkmbb.com/finance/break-even.md): Computes the contribution margin per unit and the number of units and revenue required for total revenue to equal total costs (or to reach a target profit).
- [Rule of 72 Calculator](https://tttkmbb.com/finance/rule-of-72.md): Estimates the doubling time of an amount growing at a fixed annual rate with the Rule of 72, and compares it with the exact result ln 2 / ln(1 + r) for annual compounding and ln 2 / r for continuous compounding.
- [Debt Payoff Calculator](https://tttkmbb.com/finance/debt-payoff.md): Computes how many months a fixed monthly payment takes to clear a balance charged a given APR with monthly compounding, plus the total interest paid and the size of the final payment.
- [Salary Converter](https://tttkmbb.com/finance/salary-converter.md): Converts a pay amount quoted per hour, day, week, two weeks, month or year into all the other periods, using the hours per week, days per week and paid weeks per year you specify.
- [BMI Calculator](https://tttkmbb.com/health/bmi.md): Computes body mass index (BMI) from weight and height and classifies it with the WHO adult categories, plus the healthy weight range for that height.
- [BMR Calculator](https://tttkmbb.com/health/bmr.md): Estimates basal metabolic rate (calories burned at complete rest per day) with the Mifflin-St Jeor equation, and also reports the revised Harris-Benedict estimate.
- [TDEE Calculator](https://tttkmbb.com/health/tdee.md): Estimates total daily energy expenditure from Mifflin-St Jeor BMR and an activity level, and derives calorie targets for maintaining, losing or gaining weight.
- [Body Fat Calculator](https://tttkmbb.com/health/body-fat.md): Estimates body-fat percentage from height and neck, waist (and hip for women) circumferences using the US Navy method, and classifies the result with ACE categories.
- [Ideal Weight Calculator](https://tttkmbb.com/health/ideal-weight.md): Computes ideal body weight from height and sex with the four common clinical formulas (Devine, Robinson, Miller, Hamwi) and the BMI 18.5–24.9 healthy range.
- [Water Intake Calculator](https://tttkmbb.com/health/water-intake.md): Estimates daily drinking-water needs from body weight (35 ml per kg) plus an allowance for exercise time, reported in litres, millilitres and 240 ml cups.
- [Calorie Deficit & Weight Loss Time Calculator](https://tttkmbb.com/health/calorie-deficit.md): Converts a weight change goal into total energy and the number of days and weeks required at a given daily calorie deficit or surplus, using 7,700 kcal per kilogram of body fat.
- [Macro Calculator](https://tttkmbb.com/health/macros.md): Splits a daily calorie target into grams of protein, carbohydrate and fat using a preset ratio (balanced, low-carb, high-protein, keto) or custom percentages.
- [Heart Rate Zone Calculator](https://tttkmbb.com/health/heart-rate-zones.md): Estimates maximum heart rate from age (Tanaka or Fox formula) and computes the five training zones, using the Karvonen heart-rate-reserve method when resting heart rate is supplied.
- [Pregnancy Due Date Calculator](https://tttkmbb.com/health/pregnancy-due-date.md): Estimates the due date, conception date and current gestational age from the first day of the last menstrual period, adjusting for cycle length (Naegele's rule).
- [Ovulation Calculator](https://tttkmbb.com/health/ovulation.md): Estimates the ovulation date, the six-day fertile window and the next period start from the first day of the last period and the average cycle length.
- [Waist-to-Height Ratio Calculator](https://tttkmbb.com/health/waist-to-height-ratio.md): Divides waist circumference by height and classifies the ratio using the 'keep your waist to less than half your height' guidance (NICE 2022).
- [Lean Body Mass Calculator](https://tttkmbb.com/health/lean-body-mass.md): Estimates lean body mass (fat-free mass) from weight, height and sex with the Boer (1984), James (1976) and Hume (1966) formulas.
- [Protein Intake Calculator](https://tttkmbb.com/health/protein-intake.md): Recommends a daily protein range in grams from body weight and goal (sedentary RDA 0.8 g/kg up to 1.6–2.2 g/kg for muscle gain or fat loss), based on the ISSN position stand.
- [Blood Pressure Category Calculator](https://tttkmbb.com/health/blood-pressure.md): Classifies a systolic/diastolic blood pressure reading into the ACC/AHA 2017 categories (normal, elevated, stage 1, stage 2, hypertensive crisis) and reports mean arterial and pulse pressure.
- [Body Surface Area Calculator](https://tttkmbb.com/health/body-surface-area.md): Computes body surface area in square metres from height and weight using the Mosteller and Du Bois formulas, as used for chemotherapy and other weight-independent dosing.
- [Running Pace Calculator](https://tttkmbb.com/fitness/running-pace.md): Computes running pace in min/km and min/mile and speed in km/h and mph from a distance and elapsed time, and projects the finish time for 5 km, 10 km, half marathon and marathon at that constant pace.
- [Race Time Predictor](https://tttkmbb.com/fitness/race-time-predictor.md): Predicts finish times for 5 km, 10 km, half marathon and marathon from one known race result using Riegel's endurance formula T2 = T1 × (D2/D1)^1.06, with the corresponding paces.
- [Calories Burned Calculator](https://tttkmbb.com/fitness/calories-burned.md): Estimates the calories burned during an activity from body weight, duration and the activity's MET value from the 2011 Compendium of Physical Activities, using the ACSM metabolic equation kcal/min = MET × 3.5 × kg / 200.
- [One-Rep Max Calculator](https://tttkmbb.com/fitness/one-rep-max.md): Estimates the one-repetition maximum from a weight lifted for 2–12 repetitions using the Epley, Brzycki and Lombardi equations, reports their average, and lists training loads at 95 % to 70 % of that 1RM.
- [VO2 Max Calculator](https://tttkmbb.com/fitness/vo2-max.md): Estimates maximal oxygen uptake (VO2max, ml/kg/min) from the distance covered in the Cooper 12-minute run test, and/or from the ratio of maximum to resting heart rate (Uth et al. 2004).
- [Steps to Distance Calculator](https://tttkmbb.com/fitness/steps-to-distance.md): Converts a pedometer step count into distance using a measured stride length, or a walking stride estimated from height (stride ≈ 0.414 × height).
- [Swim Pace Calculator](https://tttkmbb.com/fitness/swim-pace.md): Computes swimming pace per 100 metres and per 100 yards, speed in m/s and km/h, and the number of 25 m and 50 m pool lengths from a swum distance and time.
- [Pace Converter](https://tttkmbb.com/fitness/pace-converter.md): Converts a running pace or speed given in any one of min/km, min/mile, km/h or mph into all four units, plus seconds per km/mile and metres per second.
- [Percentage Calculator](https://tttkmbb.com/math/percentage.md): Solves the three basic percentage questions (a percentage of a number, what percentage one number is of another, and the whole behind a known part and percentage). Always returns the part, the whole and the percent.
- [Percentage Change Calculator](https://tttkmbb.com/math/percentage-change.md): Computes the relative change from an old value to a new value as a percentage, the signed absolute change, the new/old ratio and the symmetric percent difference.
- [Quadratic Equation Solver](https://tttkmbb.com/math/quadratic-equation.md): Solves ax² + bx + c = 0 with the quadratic formula, reporting the discriminant, both roots (real, or complex conjugates written as strings), the vertex of the parabola and the sum and product of the roots.
- [GCD and LCM Calculator](https://tttkmbb.com/math/gcd-lcm.md): Computes the greatest common divisor (highest common factor) and least common multiple of two or more integers with the Euclidean algorithm.
- [Prime Factorization Calculator](https://tttkmbb.com/math/prime-factorization.md): Decomposes an integer into its prime factors by trial division, tests primality, and derives the number and sum of its divisors from the exponents.
- [Factorial Calculator](https://tttkmbb.com/math/factorial.md): Computes n! = 1 × 2 × … × n for integers from 0 to 170, together with the number of decimal digits, the number of trailing zeros and a scientific-notation form.
- [Combinations and Permutations Calculator](https://tttkmbb.com/math/combinations-permutations.md): Counts the ways to choose k items from n: combinations C(n, k) when order does not matter and permutations P(n, k) when it does, with or without repetition.
- [Exponent Calculator](https://tttkmbb.com/math/exponent.md): Raises a base to any real exponent (base^exponent), including negative and fractional exponents, and reports the reciprocal and a scientific-notation form.
- [Nth Root Calculator](https://tttkmbb.com/math/nth-root.md): Computes the principal n-th root of a number (value^(1/n)), returning the real negative root for odd n and the second, negative root for even n.
- [Logarithm Calculator](https://tttkmbb.com/math/logarithm.md): Computes the logarithm of a positive number to any base using the change-of-base formula, and always reports the natural, common (base 10) and binary (base 2) logarithms.
- [Fraction Simplifier](https://tttkmbb.com/math/fraction-simplifier.md): Reduces a fraction to lowest terms by dividing by the GCD and converts it to a mixed number, a decimal and a percentage.
- [Ratio Calculator](https://tttkmbb.com/math/ratio.md): Simplifies a ratio a:b to lowest terms (decimals are scaled to integers first), expresses it as a decimal, as n:1 and as percentage shares, and optionally scales it to a new value of a.
- [Proportion Calculator](https://tttkmbb.com/math/proportion.md): Solves the proportion a / b = c / x for the unknown fourth term by cross-multiplication (x = b × c / a) and reports the common scale factor.
- [Slope Calculator](https://tttkmbb.com/math/slope.md): Computes the slope of the line through two points (rise over run), its y- and x-intercepts, the slope-intercept equation y = mx + b, the angle of inclination and the distance between the points.
- [Distance Between Two Points Calculator](https://tttkmbb.com/math/distance-2d.md): Computes the straight-line (Euclidean) distance between two points in the plane, their midpoint, the coordinate differences and the Manhattan distance.
- [Pythagorean Theorem Calculator](https://tttkmbb.com/math/pythagorean.md): Finds the missing side of a right triangle from any two of the legs a, b and hypotenuse c using a² + b² = c², and reports the area, perimeter and acute angles.
- [Rounding Calculator](https://tttkmbb.com/math/rounding.md): Rounds a number to a given number of decimal places (negative for tens, hundreds, …) or significant figures using round-half-away-from-zero, and also reports the ceiling, floor and truncated values at the same precision.
- [Arithmetic Sequence Calculator](https://tttkmbb.com/math/arithmetic-sequence.md): Computes the n-th term and the sum of the first n terms of an arithmetic progression from the first term and the common difference, and lists the first terms.
- [Geometric Sequence Calculator](https://tttkmbb.com/math/geometric-sequence.md): Computes the n-th term and the sum of the first n terms of a geometric progression from the first term and common ratio, plus the sum to infinity when |r| < 1.
- [Modulo Calculator](https://tttkmbb.com/math/modulo.md): Divides one number by another and reports the remainder under the three common sign conventions (truncated as in C/JavaScript, floored as in Python, and the non-negative Euclidean modulo) together with the integer quotient.
- [Number Base Converter](https://tttkmbb.com/math/base-converter.md): Converts an integer written in one base (2–36) to another, using exact arbitrary-precision arithmetic, and always shows the binary, octal, decimal and hexadecimal forms.
- [Scientific Notation Converter](https://tttkmbb.com/math/scientific-notation.md): Writes a number in normalised scientific notation m × 10^e with 1 ≤ |m| < 10, in E-notation, and in engineering notation (exponent a multiple of 3).
- [Circle Calculator](https://tttkmbb.com/geometry/circle.md): Computes the area, circumference, diameter and radius of a circle from either its radius or its diameter. Lengths are unit-agnostic: the area is in the square of the input unit.
- [Triangle Area Calculator](https://tttkmbb.com/geometry/triangle-area.md): Computes the area of any triangle from base and height, from three sides (Heron's formula) or from two sides and their included angle in degrees, and reports which method was used.
- [Right Triangle Calculator](https://tttkmbb.com/geometry/right-triangle.md): Solves a right triangle from any two of its sides (two legs, or one leg and the hypotenuse) using the Pythagorean theorem, and returns all sides, the two acute angles in degrees, area, perimeter and the altitude to the hypotenuse.
- [Triangle Solver](https://tttkmbb.com/geometry/triangle-solver.md): Solves a triangle from three sides (SSS) or from two sides and their included angle in degrees (SAS) with the law of cosines, returning all sides, all angles, perimeter, area, inradius, circumradius and the classification by sides and by angles.
- [Rectangle Calculator](https://tttkmbb.com/geometry/rectangle.md): Computes the area, perimeter and diagonal of a rectangle from its length and width. Lengths are unit-agnostic; the area is in the square of the input unit.
- [Trapezoid Calculator](https://tttkmbb.com/geometry/trapezoid.md): Computes the area and midsegment of a trapezoid (trapezium) from its two parallel sides and height, and the perimeter when both non-parallel legs are given.
- [Parallelogram Calculator](https://tttkmbb.com/geometry/parallelogram.md): Computes the area of a parallelogram from base and height and, when the slanted side is given, its perimeter, the acute angle between base and side in degrees, and both diagonals.
- [Regular Polygon Calculator](https://tttkmbb.com/geometry/regular-polygon.md): Computes the area, perimeter, interior and exterior angles in degrees, apothem, circumradius and number of diagonals of a regular polygon from its number of sides and side length.
- [Ellipse Calculator](https://tttkmbb.com/geometry/ellipse.md): Computes the area, approximate perimeter (Ramanujan's second approximation), eccentricity and focal distances of an ellipse from its semi-major and semi-minor axes.
- [Sphere Calculator](https://tttkmbb.com/geometry/sphere.md): Computes the volume, surface area, diameter and great-circle circumference of a sphere from its radius. The volume is in the cube and the surface area in the square of the input unit.
- [Cylinder Calculator](https://tttkmbb.com/geometry/cylinder.md): Computes the volume, base area, lateral (curved) surface area and total surface area of a right circular cylinder from its radius and height.
- [Cone Calculator](https://tttkmbb.com/geometry/cone.md): Computes the volume, slant height, base area, lateral (curved) surface area, total surface area and half-apex angle in degrees of a right circular cone from its base radius and height.
- [Rectangular Prism Calculator](https://tttkmbb.com/geometry/rectangular-prism.md): Computes the volume, total surface area, space diagonal and total edge length of a rectangular prism (cuboid or box) from its length, width and height.
- [Square Pyramid Calculator](https://tttkmbb.com/geometry/pyramid.md): Computes the volume, slant height, lateral edge, base area, lateral and total surface area and face slope in degrees of a right square pyramid from its base side and height.
- [Descriptive Statistics Calculator](https://tttkmbb.com/statistics/descriptive-statistics.md): Computes summary statistics for a list of numbers: count, sum, mean, median, mode, range, sample and population variance and standard deviation, standard error, coefficient of variation, quartiles (linear interpolation) and skewness.
- [Z-Score Calculator](https://tttkmbb.com/statistics/z-score.md): Standardises a value against a mean and standard deviation (z = (x − μ) / σ) and reports the corresponding percentile and tail probabilities under the normal distribution.
- [Normal Distribution Calculator](https://tttkmbb.com/statistics/normal-distribution.md): Computes cumulative probabilities P(X < x), P(X > x) and P(x < X < x2) and the density for a normal (Gaussian) distribution with a given mean and standard deviation.
- [Confidence Interval Calculator](https://tttkmbb.com/statistics/confidence-interval.md): Computes a confidence interval for a population mean from the sample mean, standard deviation and sample size using the normal (z) critical value: mean ± z · s / √n.
- [Sample Size Calculator](https://tttkmbb.com/statistics/sample-size.md): Computes the number of respondents needed to estimate a population proportion within a given margin of error at a given confidence level (Cochran's formula), with an optional finite population correction.
- [Margin of Error Calculator](https://tttkmbb.com/statistics/margin-of-error.md): Computes the margin of error (half-width of the confidence interval) of a sample proportion from the sample size, confidence level and observed percentage, with an optional finite population correction.
- [Binomial Distribution Calculator](https://tttkmbb.com/statistics/binomial-distribution.md): Computes the probability of exactly, at most, at least, fewer than or more than k successes in n independent trials with success probability p, plus the mean, variance and standard deviation of the distribution.
- [Poisson Distribution Calculator](https://tttkmbb.com/statistics/poisson-distribution.md): Computes the probability of exactly, at most, at least, fewer than or more than k events when events occur independently at a constant average rate λ per interval, plus the mean, variance and standard deviation.
- [Probability of Two Events Calculator](https://tttkmbb.com/statistics/probability-of-events.md): Combines the probabilities of two events A and B that are either independent or mutually exclusive into the probabilities of both, at least one, exactly one, one but not the other, and neither occurring.
- [Correlation Coefficient Calculator](https://tttkmbb.com/statistics/correlation.md): Computes the Pearson product-moment correlation coefficient r, the coefficient of determination r², and the sample covariance for two paired lists of numbers, with a strength/direction interpretation.
- [Linear Regression Calculator](https://tttkmbb.com/statistics/linear-regression.md): Fits an ordinary least-squares line to paired (x, y) data and returns the slope, intercept, equation, Pearson r, R², the standard error of the estimate and an optional prediction for a new x.
- [Weighted Average Calculator](https://tttkmbb.com/statistics/weighted-average.md): Computes the weighted arithmetic mean Σ(w·x) / Σw of a list of values and a matching list of weights, along with the total weight and the unweighted mean for comparison.
- [Percentile Calculator](https://tttkmbb.com/statistics/percentile.md): For a list of numbers, computes the value at a given percentile (linear interpolation, as in Excel PERCENTILE.INC) and/or the percentile rank of a given value (percentage of values below it, counting ties as half).
- [Expected Value Calculator](https://tttkmbb.com/statistics/expected-value.md): Computes the expected value E[X] = Σ x·p(x), the variance and the standard deviation of a discrete random variable from its list of outcomes and their probabilities.
- [Length Converter](https://tttkmbb.com/conversion/length.md): Converts a length or distance between metric (nm to km), imperial/US (in, ft, yd, mi), nautical and astronomical units using exact NIST factors (1 in = 0.0254 m, 1 mi = 1609.344 m).
- [Mass / Weight Converter](https://tttkmbb.com/conversion/mass.md): Converts mass between metric units (μg to tonne), avoirdupois units (grain, oz, lb, stone, short and long ton) and carats using the exact definition 1 lb = 0.45359237 kg.
- [Temperature Converter](https://tttkmbb.com/conversion/temperature.md): Converts temperatures between Celsius, Fahrenheit, Kelvin and Rankine with the exact defining relations (°F = °C × 9/5 + 32, K = °C + 273.15, °R = °F + 459.67) and rejects values below absolute zero.
- [Area Converter](https://tttkmbb.com/conversion/area.md): Converts areas between metric (mm² to km², hectare) and US/imperial units (in², ft², yd², acre, mi²) using exact factors (1 ft² = 0.09290304 m², 1 acre = 4046.8564224 m²).
- [Volume Converter](https://tttkmbb.com/conversion/volume.md): Converts volumes between metric units (mL, L, cm³, m³), US customary units (tsp to gallon, in³, ft³, yd³, oil barrel), imperial units (fl oz, pint, quart, gallon) and metric kitchen units, with exact definitions (1 US gal = 3.785411784 L, 1 imperial gal = 4.54609 L).
- [Speed Converter](https://tttkmbb.com/conversion/speed.md): Converts speeds between m/s, km/h, km/s, mph, ft/s, knots and Mach number using exact factors (1 mph = 0.44704 m/s, 1 kn = 1852/3600 m/s) and 340.294 m/s for Mach 1 at sea level.
- [Time Converter](https://tttkmbb.com/conversion/time.md): Converts durations between nanoseconds, microseconds, milliseconds, seconds, minutes, hours, days, weeks, fortnights, 30-day months, 365-day years and Julian years (365.25 days).
- [Data Storage Converter](https://tttkmbb.com/conversion/data-storage.md): Converts digital storage and transfer sizes between bits, bytes, decimal SI multiples (KB = 1000 B, MB, GB, TB, PB), binary IEC multiples (KiB = 1024 B, MiB, GiB, TiB, PiB) and kilobit/megabit/gigabit/terabit.
- [Energy Converter](https://tttkmbb.com/conversion/energy.md): Converts energy between joules (J to GJ), calories (thermochemical cal = 4.184 J, kcal), watt-hours (Wh, kWh, MWh), BTU (International Table, 1055.05585262 J), MMBTU, therm (EC), electronvolts, ergs and foot-pounds.
- [Pressure Converter](https://tttkmbb.com/conversion/pressure.md): Converts pressure between pascals (Pa to MPa), bar/millibar, standard atmospheres, psi and ksi, millimetres and inches of mercury, torr and technical atmospheres (kgf/cm²) using NIST factors (1 psi = 6894.757293168 Pa, 1 atm = 101325 Pa).
- [Power Converter](https://tttkmbb.com/conversion/power.md): Converts power between watts (W to GW), mechanical horsepower (745.69987158227 W), metric horsepower (735.49875 W), BTU per hour, foot-pounds per second, kcal/h and tons of refrigeration.
- [Angle Converter](https://tttkmbb.com/conversion/angle.md): Converts plane angles between degrees, radians, milliradians, gradians (gon), arcminutes, arcseconds and turns (revolutions) using π rad = 180° = 200 gon = 0.5 turn.
- [Fuel Economy Converter](https://tttkmbb.com/conversion/fuel-economy.md): Converts fuel consumption between litres per 100 km, kilometres per litre, miles per US gallon and miles per imperial gallon; L/100km is the base and the mpg relations are reciprocal (L/100km = 235.214583 / mpg_US).
- [Force Converter](https://tttkmbb.com/conversion/force.md): Converts force between newtons (N, kN), dynes, gram-force, kilogram-force (kilopond), ounce-force, pound-force and kips using exact factors (1 lbf = 4.4482216152605 N, 1 kgf = 9.80665 N).
- [Frequency Converter](https://tttkmbb.com/conversion/frequency.md): Converts frequency and rotational speed between hertz (Hz to THz), revolutions per minute, beats per minute, radians per second (angular frequency, ω = 2πf) and degrees per second.
- [Density Converter](https://tttkmbb.com/conversion/density.md): Converts density between kg/m³, g/cm³, g/mL, kg/L, g/L, mg/L, lb/ft³, lb/in³, oz/in³ and lb per US gallon using exact mass and volume definitions (1 lb/ft³ = 16.01846337 kg/m³).
- [Torque Converter](https://tttkmbb.com/conversion/torque.md): Converts torque (moment of force) between N·m, kN·m, N·cm, mN·m, lbf·ft, lbf·in, kgf·m, kgf·cm and ozf·in using exact force and length definitions (1 lbf·ft = 1.3558179483 N·m).
- [Cooking Measurement Converter](https://tttkmbb.com/conversion/cooking-measurements.md): Converts kitchen volume measures between US customary teaspoons, tablespoons, fluid ounces, cups, pints, quarts and gallons, metric teaspoons (5 mL), tablespoons (15 mL) and cups (250 mL), imperial fluid ounces and pints, and millilitres/litres.
- [Speed, Distance & Time Calculator](https://tttkmbb.com/physics/speed-distance-time.md): Solves the uniform-motion relation speed = distance / time for whichever of the three quantities is omitted, and reports the speed in m/s, km/h and mph and the time as h:mm:ss.
- [Acceleration Calculator](https://tttkmbb.com/physics/acceleration.md): Computes average acceleration from initial velocity, final velocity and elapsed time, plus the velocity change, the distance covered assuming constant acceleration, and the acceleration expressed in g.
- [Force Calculator](https://tttkmbb.com/physics/newtons-second-law.md): Computes net force from mass and acceleration with Newton's second law, reported in newtons, kilonewtons and pounds-force, together with the object's weight under standard gravity.
- [Kinetic Energy Calculator](https://tttkmbb.com/physics/kinetic-energy.md): Computes the translational kinetic energy of a moving mass from KE = ½·m·v², reported in joules, kilojoules, kilowatt-hours and kilocalories.
- [Potential Energy Calculator](https://tttkmbb.com/physics/potential-energy.md): Computes the gravitational potential energy of a mass raised to a height near a planet's surface with PE = m·g·h (standard gravity by default), and the speed the mass would reach if it fell that height freely.
- [Work & Power Calculator](https://tttkmbb.com/physics/work-power.md): Computes the mechanical work done by a constant force over a displacement, allowing for the angle between force and motion, and the average power when the duration is supplied.
- [Momentum Calculator](https://tttkmbb.com/physics/momentum.md): Computes linear momentum from mass and velocity, the matching kinetic energy, and, when a stopping time is given, the average force needed to bring the object to rest (impulse–momentum theorem).
- [Free Fall Calculator](https://tttkmbb.com/physics/free-fall.md): Computes the time to fall a given height from rest, or the height fallen in a given time, together with the final (impact) velocity, using h = ½·g·t² with no air resistance.
- [Projectile Motion Calculator](https://tttkmbb.com/physics/projectile-motion.md): Computes time of flight, horizontal range, maximum height and impact speed for a projectile launched at a given speed and angle from an optional initial height, ignoring air resistance (closed-form kinematics).
- [Ohm's Law Calculator](https://tttkmbb.com/physics/ohms-law.md): Solves Ohm's law V = I·R for whichever of voltage, current or resistance is omitted and reports the electrical power dissipated (P = V·I).
- [Electric Power Calculator](https://tttkmbb.com/physics/electric-power.md): Computes electrical power from voltage and current (or the current drawn by a known power at a given voltage), the equivalent resistance, and, with hours of use and a tariff, the energy in kWh and its cost.
- [Density Calculator](https://tttkmbb.com/physics/density-mass-volume.md): Solves ρ = m / V for whichever of density, mass or volume is omitted, and reports density in kg/m³ and g/cm³, volume in litres and cm³, and the specific gravity relative to water.
- [Pressure Calculator](https://tttkmbb.com/physics/pressure-force-area.md): Computes pressure as force divided by the area it acts on, and reports it in pascals, kilopascals, bar, pounds per square inch and standard atmospheres.
- [Wavelength & Frequency Calculator](https://tttkmbb.com/physics/wavelength-frequency.md): Converts between wavelength and frequency for a wave of known propagation speed (default: the speed of light in vacuum) and, for electromagnetic waves in vacuum, reports the photon energy E = h·f in joules and electronvolts.
- [Pendulum Period Calculator](https://tttkmbb.com/physics/pendulum.md): Computes the period, frequency and angular frequency of a simple pendulum from its length with the small-angle formula T = 2π√(L/g); when an amplitude is given it also returns the exact period from the arithmetic–geometric mean.
- [Hooke's Law Calculator](https://tttkmbb.com/physics/hookes-law.md): Computes the restoring force of a linear spring and the elastic potential energy stored at a given displacement, plus the natural period and frequency of a mass on that spring when a mass is supplied.
- [Gravitational Force Calculator](https://tttkmbb.com/physics/gravitational-force.md): Computes the attractive gravitational force between two point or spherically symmetric masses at a given centre-to-centre distance with Newton's law and the CODATA 2018 value of G, plus the acceleration each mass experiences.
- [Centripetal Force Calculator](https://tttkmbb.com/physics/centripetal-force.md): Computes the centripetal (centre-seeking) force and acceleration needed to keep a mass moving in a circle of given radius at a given speed, plus the angular velocity, rotation period and rpm.
- [Specific Heat Calculator](https://tttkmbb.com/physics/specific-heat.md): Computes the heat energy needed to change the temperature of a mass of material by a given amount from Q = m·c·ΔT, using the specific heat capacity of liquid water (4186 J/(kg·K)) by default.
- [Resistors in Series and Parallel Calculator](https://tttkmbb.com/physics/resistors-series-parallel.md): Computes the equivalent resistance of a list of resistors connected all in series (sum) and all in parallel (reciprocal of the sum of reciprocals), plus the parallel conductance.
- [Molar Mass Calculator](https://tttkmbb.com/chemistry/molar-mass.md): Parses a chemical formula (including brackets, nested groups and hydrates) and sums IUPAC 2021 standard atomic weights to give the molar mass in g/mol, plus the atom count and mass-percent composition of each element.
- [Moles to Grams Calculator](https://tttkmbb.com/chemistry/moles-mass.md): Converts between mass in grams and amount in moles using the molar mass (from a formula or given directly), and reports the number of molecules or formula units from the Avogadro constant. Any two of molar mass, mass and moles give the third.
- [Molarity Calculator](https://tttkmbb.com/chemistry/molarity.md): Computes molar concentration (mol/L) of a solution from the amount of solute (moles, or mass with a formula or molar mass) and the solution volume, or the moles and mass of solute needed to prepare a target molarity.
- [Dilution Calculator](https://tttkmbb.com/chemistry/dilution.md): Applies the dilution equation C1·V1 = C2·V2 to find the missing one of stock concentration, stock volume, final concentration or final volume, plus the solvent to add and the dilution factor.
- [Ideal Gas Law Calculator](https://tttkmbb.com/chemistry/ideal-gas-law.md): Solves the ideal gas equation PV = nRT for whichever of pressure, volume, amount or temperature is left empty, with pressure in atm, kPa, bar, mmHg or psi and temperature in °C, K or °F.
- [pH Calculator](https://tttkmbb.com/chemistry/ph.md): Converts between pH, pOH, hydrogen-ion concentration and hydroxide-ion concentration at 25 °C (Kw = 1.0×10⁻¹⁴) from any one of them, and classifies the solution as acidic, neutral or basic.
- [Half-Life Calculator](https://tttkmbb.com/chemistry/half-life.md): Computes first-order exponential decay: given two of half-life, elapsed time and remaining amount (with an initial amount) it solves the third and reports the remaining fraction, number of half-lives, decay constant and mean lifetime.
- [Percent Yield Calculator](https://tttkmbb.com/chemistry/percent-yield.md): Divides the actual (experimental) yield by the theoretical yield to give percent yield, plus the amount and percentage of product lost.
- [Mass Percent Calculator](https://tttkmbb.com/chemistry/mass-percent.md): Computes the mass percent (% w/w) of a solute from the solute mass and either the total solution mass or the solvent mass, and expresses the same concentration as mass fraction, parts per million and parts per billion.
- [Henderson–Hasselbalch Calculator](https://tttkmbb.com/chemistry/henderson-hasselbalch.md): Computes the pH of a buffer from the acid's pKa and the concentrations (or ratio) of conjugate base and weak acid with the Henderson–Hasselbalch equation, or the base/acid ratio required for a target pH.
- [Age Calculator](https://tttkmbb.com/everyday/age.md): Computes the exact age on a given date as years, months and days by Gregorian calendar arithmetic, plus total days and weeks, the weekday of birth, and the date of and days until the next birthday.
- [Date Difference Calculator](https://tttkmbb.com/everyday/date-difference.md): Counts the days between two ISO dates and expresses the gap as weeks and days, as a calendar breakdown in years, months and days, and as business days (Monday–Friday, public holidays not excluded).
- [Add or Subtract Days Calculator](https://tttkmbb.com/everyday/add-days.md): Adds a signed number of days to an ISO date and returns the resulting date and its weekday, using Gregorian calendar arithmetic in UTC.
- [Days Until Calculator](https://tttkmbb.com/everyday/days-until.md): Counts the days from a reference date (default today) to a target date and reports the countdown as weeks and days, approximate months, a calendar breakdown and the target's weekday.
- [Day of the Week Calculator](https://tttkmbb.com/everyday/day-of-week.md): Returns the weekday of any Gregorian date together with its day-of-year number, the ISO 8601 week number and week-based year, and whether it falls on a weekend.
- [Time Duration Calculator](https://tttkmbb.com/everyday/time-duration.md): Computes the elapsed time between a start and an end clock time (24-hour HH:MM), optionally minus a break, handling intervals that cross midnight, and reports it as hours and minutes and as decimal hours.
- [Fuel Cost Calculator](https://tttkmbb.com/everyday/fuel-cost.md): Estimates the fuel needed for a trip and its cost from distance, fuel consumption in litres per 100 km and the price per litre, with the cost per person when it is shared.
- [Electricity Cost Calculator](https://tttkmbb.com/everyday/electricity-cost.md): Converts an appliance's power draw and daily usage into kilowatt-hours and the running cost per day, over a chosen number of days, per 30-day month and per 365-day year, using the US DOE energy-use formula.
- [Bill Split Calculator](https://tttkmbb.com/everyday/bill-split.md): Adds an optional tip percentage to a bill and divides the total equally among a number of people, reporting the tip, the total and each person's share.
- [Unit Price Comparison Calculator](https://tttkmbb.com/everyday/unit-price.md): Divides each price by its quantity to get the price per unit, tells which of two options is cheaper per unit and by what percentage.
- [Reading Time Calculator](https://tttkmbb.com/everyday/reading-time.md): Estimates how long a text takes to read silently from its word count and a reading speed, defaulting to 238 words per minute, the adult mean for non-fiction found in Brysbaert's 2019 meta-analysis; also gives the read-aloud time at 183 wpm.
- [Typing Speed Calculator](https://tttkmbb.com/everyday/typing-speed.md): Computes gross words per minute from characters typed (one word = 5 characters) or from a word count, then net WPM after penalising uncorrected errors, plus accuracy and characters per minute.
- [GPA Calculator](https://tttkmbb.com/everyday/gpa.md): Computes a grade point average as the credit-weighted mean of course grade points (quality points divided by total credits), with an unweighted average when credits are omitted, and the nearest US letter grade on the 4.0 scale.
- [Final Grade Calculator](https://tttkmbb.com/everyday/final-grade.md): Solves the weighted-average grade equation for the final exam score required to reach a desired overall grade, given the current grade and the final's weight, and reports whether that score is achievable.
- [Sleep Cycle Calculator](https://tttkmbb.com/everyday/sleep-cycles.md): Suggests bedtimes for a given wake-up time, or wake-up times for a given bedtime, so that sleep ends at the boundary of a full sleep cycle (default 90 minutes) after a typical time to fall asleep (default 14 minutes).
- [Aspect Ratio Calculator](https://tttkmbb.com/everyday/aspect-ratio.md): Reduces a width and height to their simplest ratio and decimal value, identifies the closest common ratio (16:9, 4:3, 3:2, 21:9 …) and scales the dimensions to a new width or height while keeping the ratio.
- [Download Time Calculator](https://tttkmbb.com/everyday/download-time.md): Computes how long a file transfer takes from the file size (MB, GB, TB) and the connection speed (Mbit/s, MB/s or Gbit/s), converting bytes to bits at 8 bits per byte with decimal (SI) prefixes.
- [Leap Year Calculator](https://tttkmbb.com/everyday/leap-year.md): Applies the Gregorian leap-year rule (divisible by 4, except centuries not divisible by 400) to a year and reports the reason, the number of days in the year and in February, and the next and previous leap years.
- [Roman Numeral Converter](https://tttkmbb.com/everyday/roman-numeral.md): Converts an integer from 1 to 3999 into standard (subtractive-notation) Roman numerals, or parses a Roman numeral back into a number, and shows the value of each symbol group.
- [Work Hours Calculator](https://tttkmbb.com/everyday/work-hours.md): Derives paid hours per day from shift start and end times minus unpaid breaks, scales them to a week (working days), an average month (52/12 weeks) and a year (52 weeks), and multiplies by an optional hourly rate for pay.
- [Recipe Scaler](https://tttkmbb.com/food/recipe-scaler.md): Computes the conversion factor between an original and a desired number of servings and multiplies a list of ingredient amounts by it.
- [Cooking Measurement Converter](https://tttkmbb.com/food/cooking-converter.md): Converts a kitchen volume between US customary units (teaspoon, tablespoon, fluid ounce, cup, pint, quart), the 250 ml metric cup, millilitres and litres using the exact US definitions.
- [Coffee Ratio Calculator](https://tttkmbb.com/food/coffee-ratio.md): Computes the grams of ground coffee for a given amount of water (or the water for a given dose) from a brew ratio, using method-specific default ratios (drip and pour-over 1:16, French press 1:15, AeroPress 1:13, cold brew concentrate 1:8, espresso 1:2) or a custom ratio.
- [Calories from Macros Calculator](https://tttkmbb.com/food/calories-from-macros.md): Converts grams of protein, carbohydrate, fat and alcohol into kilocalories and kilojoules with the Atwater general factors (4 / 4 / 9 / 7 kcal per gram) and reports each macronutrient's share of total energy.
- [Pizza Dough Calculator](https://tttkmbb.com/food/pizza-dough.md): Computes the flour, water, salt, yeast and oil in grams for a number of pizza dough balls of a given weight from baker's percentages (hydration, salt, yeast, oil as % of flour).
- [Brine Calculator](https://tttkmbb.com/food/brine.md): Computes the grams of salt (and optional sugar) for a wet brine from the water volume and a percentage concentration expressed relative to the water weight (6 % = 60 g per litre).
- [Rice to Water Ratio Calculator](https://tttkmbb.com/food/rice-water.md): Computes the water needed for a quantity of uncooked rice (cups or grams) using absorption-method ratios by rice type: long-grain white 1:1.5, jasmine 1:1.25, basmati 1:1.5, brown 1:2, sushi 1:1.1, wild 1:3.
- [Baker's Percentage Calculator](https://tttkmbb.com/food/bakers-percentage.md): Converts a bread or dough formula between baker's percentages and grams: flour is 100 %, every other ingredient is expressed relative to flour weight; works in both directions and reports total dough weight and hydration.
- [Turkey Cooking Time Calculator](https://tttkmbb.com/food/turkey-cooking-time.md): Looks up the USDA FSIS roasting timetable for a whole turkey at 325 °F (163 °C) by weight and stuffing, returning the time range in minutes, the 165 °F (74 °C) safe internal temperature and refrigerator thawing time.
- [Flooring Calculator](https://tttkmbb.com/construction/flooring.md): Computes the floor area of a rectangular room, adds a cutting-waste allowance and converts the result into the number of boxes to buy from the coverage printed on the packaging. Areas are reported in m² and ft².
- [Paint Calculator](https://tttkmbb.com/construction/paint.md): Estimates wall paint from the wall area (room length, width and height, or a given area), subtracting 1.9 m² per door and 1.4 m² per window, multiplying by the number of coats and dividing by the coverage rate; reports litres, US gallons and cans.
- [Concrete Slab Calculator](https://tttkmbb.com/construction/concrete-slab.md): Computes the concrete volume of a rectangular slab, footing or pad from length, width and thickness, adds a waste allowance and converts it to cubic yards, cubic feet and the number of 80 lb, 60 lb and 25 kg bags of premixed concrete.
- [Tile Calculator](https://tttkmbb.com/construction/tile.md): Counts the tiles needed for a floor or wall area from the tile dimensions plus the grout joint width, adds a cutting-waste allowance and converts to boxes when the tiles per box are known.
- [Roof Pitch Calculator](https://tttkmbb.com/construction/roof-pitch.md): Converts a roof slope given as rise and run, or as an angle, into the pitch expressed in rise per 12 units of run, the angle in degrees, the slope in percent and the rafter length multiplier (rafter length per unit of horizontal run).
- [Stair Calculator](https://tttkmbb.com/construction/stairs.md): Divides a total floor-to-floor rise into equal risers close to a target riser height, derives the tread count, total run, stringer length and stair angle, and checks the result against the IRC residential limits (riser ≤ 7¾ in / 196 mm, tread ≥ 10 in / 254 mm) and the 2R + T comfort rule.
- [Wallpaper Calculator](https://tttkmbb.com/construction/wallpaper.md): Estimates wallpaper rolls by the strip method: the strip length is the wall height plus 10 cm trim, rounded up to a whole pattern repeat; whole strips per roll are counted, door and window areas are deducted and the strips are converted to rolls.
- [Gravel Calculator](https://tttkmbb.com/construction/gravel.md): Computes the volume of loose aggregate needed to cover an area to a given depth and converts it to weight with a typical bulk density for gravel, crushed stone, sand, topsoil or mulch (or a custom density).
- [Drywall Calculator](https://tttkmbb.com/construction/drywall.md): Estimates the number of gypsum board sheets for walls (and optionally the ceiling) of a room with a waste allowance, plus screws at about one per square foot and joint compound at the USG rate of 10 gallons per 1,000 ft² of board.
- [Fence Calculator](https://tttkmbb.com/construction/fence.md): Estimates the posts, rails and pickets for a straight run of wooden fence from the total length, the maximum post spacing, the number and width of gates, the rails per section and the picket width plus gap.
- [Decking Calculator](https://tttkmbb.com/construction/decking.md): Estimates the number of deck boards (rows of boards across the width, board lengths along the length, plus waste), the joists at a given spacing and the screws at two per board per joist for a rectangular deck.
- [Board Feet Calculator](https://tttkmbb.com/construction/board-feet.md): Computes board feet (the US lumber volume unit: 1 board foot = 144 cubic inches = a 1 in × 12 in × 12 in board) from nominal thickness and width in inches and length in feet, for a given quantity, with the total cost at a price per board foot.
- [Brick Calculator](https://tttkmbb.com/construction/brick.md): Counts the bricks in a single-leaf (half-brick, stretcher-bond) wall from its length and height using a standard brick size with its mortar joint, adds waste, and estimates the mortar volume geometrically and the bags of mortar mix from a manufacturer rule of thumb.