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Calories from Macros Calculator

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.

When to use

You have the macronutrient grams of a food, meal or daily intake and need total calories or the percentage split, e.g. to check a food label or diet plan.

Do not use when: You want to go the other way, from a calorie target to gram targets (use macros), or need calorie needs (use tdee).

Formula

kcal = 4·protein_g + 4·(carbs_g − fiber_g) + 2·fiber_g + 9·fat_g + 7·alcohol_g; percent_x = kcal_x / kcal × 100; kJ = kcal × 4.184

Atwater general factors are averages of metabolisable energy; label values can differ by a few percent because manufacturers may use specific factors, and US labels may count insoluble fibre at 0 kcal/g.

Inputs

Parameter	Type	Unit	Required	Description
`protein_g`	number	g	yes	Protein in grams. Range: ≥ 0, ≤ 5000
`carbs_g`	number	g	yes	Total carbohydrate in grams, including any fibre. Range: ≥ 0, ≤ 5000
`fat_g`	number	g	yes	Fat in grams. Range: ≥ 0, ≤ 5000
`alcohol_g`	number	g	default 0	Ethanol in grams (a 330 ml 5 % beer contains about 13 g). Range: ≥ 0, ≤ 1000
`fiber_g`	number	g	no	Optional fibre included in carbs_g; counted at 2 kcal/g (EU labelling factor) instead of 4 kcal/g. Range: ≥ 0, ≤ 1000

Outputs

Output	Type	Unit	Description
`calories_kcal`	number	kcal	Sum of all macronutrient energy.
`energy_kj`	number	kJ	Total energy in kilojoules (× 4.184).
`protein_kcal`	number	kcal	protein_g × 4.
`carbs_kcal`	number	kcal	(carbs_g − fiber_g) × 4 + fiber_g × 2.
`fat_kcal`	number	kcal	fat_g × 9.
`alcohol_kcal`	number	kcal	alcohol_g × 7.
`protein_percent`	number	%	Protein energy as a percentage of total energy.
`carbs_percent`	number	%	Carbohydrate energy as a percentage of total energy.
`fat_percent`	number	%	Fat energy as a percentage of total energy.
`alcohol_percent`	number	%	Alcohol energy as a percentage of total energy.

Example

30 g protein, 40 g carbs, 10 g fat: {"protein_g":30,"carbs_g":40,"fat_g":10} → {"calories_kcal":370,"energy_kj":1548,"protein_kcal":120,"carbs_kcal":160,"fat_kcal":90,"protein_percent":32.4,"carbs_percent":43.2,"fat_percent":24.3,"alcohol_percent":0}

25 / 50 / 15 g plus 14 g alcohol: {"protein_g":25,"carbs_g":50,"fat_g":15,"alcohol_g":14} → {"calories_kcal":533,"alcohol_kcal":98,"alcohol_percent":18.4,"carbs_percent":37.5}

GET https://tttkmbb.com/api/v1/calculate/calories-from-macros?protein_g=30&carbs_g=40&fat_g=10

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/calories-from-macros (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/calories-from-macros · Markdown: https://tttkmbb.com/food/calories-from-macros.md · JSON definition: https://tttkmbb.com/food/calories-from-macros.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="calories-from-macros"
OpenAPI operationId: calculate_calories_from_macros
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Why does the label show fewer calories than this?

Labels may subtract insoluble fibre entirely (US) or use specific Atwater factors for the food; rounding rules also allow small differences.

Does 'net carbs' apply here?

Only via fiber_g: fibre is counted at 2 kcal/g. Sugar alcohols are not handled separately (they average about 2.4 kcal/g).

Related calculators

Macro Calculator — Reverse direction: grams of each macro from a calorie target.
TDEE Calculator — Compare the intake with daily energy needs.