# Burn Rate and Runway Calculator

> Computes gross burn, net burn (expenses minus revenue) and the runway in months from a cash balance, and the projected date the cash runs out when a start date is given.

- Calculator id: `burn-rate-runway` · Category: Business & Marketing (`business`) · Tool name: `calculate_burn_rate_runway`
- Canonical page: https://tttkmbb.com/business/burn-rate-runway · This document: https://tttkmbb.com/business/burn-rate-runway.md · JSON definition: https://tttkmbb.com/business/burn-rate-runway.json

## Purpose

Computes gross burn, net burn (expenses minus revenue) and the runway in months from a cash balance, and the projected date the cash runs out when a start date is given.

**Use when:** You are a startup or project with a fixed cash pile and want to know how long it lasts at current spending and revenue.

**Do not use when:** Revenue or costs change month to month (model each month separately) or you need a loan payoff or savings timeline (use debt-payoff or savings-goal).

## Input

| Parameter | Type | Unit | Required | Description |
| --- | --- | --- | --- | --- |
| `cash_balance` | number |  | required | Cash and equivalents available today. (min 0, max 10000000000000) |
| `monthly_expenses` | number |  | required | Total cash spent per month (salaries, rent, tools, marketing). (min 0, max 1000000000000) |
| `monthly_revenue` | number |  | optional, default 0 | Cash received per month; 0 for a pre-revenue company. (min 0, max 1000000000000) |
| `start_date` | date |  | optional | Optional date of the cash balance (YYYY-MM-DD); enables the zero-cash date. |

## Output

| Field | Type | Unit | Description |
| --- | --- | --- | --- |
| `gross_burn_per_month` | number |  | monthly_expenses. |
| `net_burn_per_month` | number |  | monthly_expenses − monthly_revenue (negative means cash-flow positive). |
| `runway_months` | number | months | cash_balance / net burn (only when net burn > 0). |
| `months_of_expenses_covered` | number | months | cash_balance / gross burn, i.e. runway if all revenue stopped (only when expenses > 0). |
| `zero_cash_date` | date |  | start_date + runway_months × 365.25/12 days (only when start_date given and net burn > 0). |
| `runway_status` | string |  | Plain-language summary. |

## Formula

`net_burn = monthly_expenses − monthly_revenue; runway_months = cash_balance / net_burn; zero_cash_date = start_date + runway_months × 30.4375 days`

Assumes constant monthly expenses and revenue; the 'default alive' test would instead grow revenue at its current rate. Common guidance is to start fundraising with at least 6–9 months of runway left.

## Data Sources

- Wikipedia – Burn rate — https://en.wikipedia.org/wiki/Burn_rate (reference, retrieved 2026-09-24)
- Investopedia – Burn Rate: What It Means and How to Calculate It — https://www.investopedia.com/terms/b/burnrate.asp (reference, retrieved 2026-09-24)
- Andreessen Horowitz – 16 Startup Metrics — https://a16z.com/16-startup-metrics/ (reference, retrieved 2026-09-24)

Data freshness: `static`. Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output.

## API

- `GET https://tttkmbb.com/api/v1/calculate/burn-rate-runway?cash_balance=…&monthly_expenses=…`
- `POST https://tttkmbb.com/api/v1/calculate/burn-rate-runway` with JSON body `{"inputs": {…}}`
- Response: unified envelope (`success`, `request`, `result.values`, `result.units`, `sources`, `freshness`, `timestamp`, `next_actions`, `links`); see https://tttkmbb.com/docs/response-format.md
- Schema: https://tttkmbb.com/api/v1/calculators/burn-rate-runway · OpenAPI operationId `calculate_burn_rate_runway` in https://tttkmbb.com/openapi.json
- Authentication: none. Rate limit: fair use, see https://tttkmbb.com/docs/rate-limits.md.

## MCP

- Server: `https://tttkmbb.com/mcp` (Streamable HTTP, JSON-RPC 2.0, no auth)
- Tool:  `run_calculator` with `{"calculator_id": "burn-rate-runway", "inputs": {…}}`

## Example

- 500,000 cash, 60,000 expenses, 20,000 revenue from 2026-01-01: inputs `{"cash_balance":500000,"monthly_expenses":60000,"monthly_revenue":20000,"start_date":"2026-01-01"}` → `{"gross_burn_per_month":60000,"net_burn_per_month":40000,"runway_months":12.5,"months_of_expenses_covered":8.33,"zero_cash_date":"2027-01-16"}`
- 120,000 cash, 25,000 expenses, no revenue: inputs `{"cash_balance":120000,"monthly_expenses":25000}` → `{"net_burn_per_month":25000,"runway_months":4.8,"months_of_expenses_covered":4.8}`

```
GET https://tttkmbb.com/api/v1/calculate/burn-rate-runway?cash_balance=500000&monthly_expenses=60000&monthly_revenue=20000&start_date=2026-01-01
```

## Limitations

Revenue or costs change month to month (model each month separately) or you need a loan payoff or savings timeline (use debt-payoff or savings-goal). Assumes constant monthly expenses and revenue; the 'default alive' test would instead grow revenue at its current rate. Common guidance is to start fundraising with at least 6–9 months of runway left. All values are computed from the formula above; no measurement or live data is involved.

## FAQ

**Gross or net burn?**

Gross burn is total spending; net burn subtracts revenue and determines runway. Investors usually quote net burn.

**What if revenue exceeds expenses?**

Net burn is negative, the company is cash-flow positive and runway is unlimited; the calculator reports that status instead of a number.

## Related

- [MRR Growth Calculator](https://tttkmbb.com/business/mrr-growth.md) — Project the revenue side over the same months.
- [Add or Subtract Days Calculator](https://tttkmbb.com/everyday/add-days.md) — Date arithmetic for a specific number of days.
- [Break-Even Calculator](https://tttkmbb.com/finance/break-even.md) — Sales volume at which burn reaches zero.