Macronutrient & Calorie Calculator
Turn macronutrients into calories, or a calorie target into macronutrient grams. Food energy comes from four sources with standard energy densities — protein and carbohydrate at 4 kcal per gram, fat at 9, and alcohol at 7 — known as the Atwater factors. Enter grams to see total calories and the percentage each macro contributes, or enter a daily calorie target with a protein/carb/fat split to get the grams to aim for. Provided for informational and educational use, not as dietary or medical advice.
How to use this tool
- Choose a mode: grams to calories, or a calorie target to grams.
- For grams mode, enter protein, carbohydrate, fat and (optionally) alcohol in grams.
- For target mode, enter your daily calorie target and a protein/carb/fat percentage split.
- Read the total calories with the per-macro breakdown, or the gram targets.
- These use standard energy values and are informational, not dietary advice.
The formula
Food energy comes from four macronutrients, each with a standard energy density (the Atwater factors). Multiplying grams by these factors gives calories; dividing a calorie target by them turns a percentage split back into grams.
calories = 4·protein_g + 4·carb_g + 9·fat_g + 7·alcohol_g
grams = (calories × macro%) ÷ energy_per_gram- protein/carb
- 4 kcal per gram
- fat
- 9 kcal per gram
- alcohol
- 7 kcal per gram
These are standard average energy values. Fibre and sugar alcohols yield less than the 4 kcal/g rule implies, so labelled calorie counts can differ slightly from this estimate.
Worked examples
From grams
- Given
- 150 P, 200 C, 60 F
- Result
- 1940 kcal
150×4 + 200×4 + 60×9 = 600 + 800 + 540 = 1940 kcal, about 31% protein.
From target
- Given
- 2000 kcal at 30/40/30
- Result
- 150 P, 200 C, 67 F (g)
Protein 600 kcal ÷ 4 = 150 g; carbs 800 ÷ 4 = 200 g; fat 600 ÷ 9 ≈ 67 g.
Alcohol
- Given
- 1 g alcohol
- Result
- 7 kcal
Alcohol carries 7 kcal per gram — nearly as energy-dense as fat.
Frequently asked questions
By the standard Atwater factors: protein and carbohydrate each provide 4 kcal per gram, fat provides 9, and alcohol 7. Fat is the most energy-dense of the foods, which is why small amounts add up quickly. These are the values this calculator uses.
Alcohol is metabolised for energy at about 7 kcal per gram — close to fat and well above protein or carbs. It is often left out of macro tracking, but it contributes real calories, so the tool includes it as an optional input.
There is no single right answer — it depends on your goals, activity and preferences. A common balanced starting point is 30% protein, 40% carbohydrate, 30% fat, but athletes, low-carb dieters and others use very different ratios. The tool lets you set any split and see the resulting grams.
Labels can differ for a few reasons: fibre and sugar alcohols yield less than 4 kcal per gram, rounding on labels, and manufacturers sometimes using slightly different factors. The Atwater values here are the standard general-purpose estimate, so expect small differences from specific packaged foods.
No. It is a calculator using standard energy values, provided for informational and educational purposes. It does not account for your individual health, and it is not a substitute for guidance from a registered dietitian or doctor, especially for medical conditions or restrictive dieting.
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