Macro Calculator
Calculate daily carbohydrate, protein, and fat gram targets from your daily calorie target and macro percentage split, using standard 4/4/9 kcal-per-gram energy conversion.
How It's Calculated
Formula
\text{carb g} = \dfrac{\text{calories} \times \text{carb\%}}{100 \times 4}
\text{protein g} = \dfrac{\text{calories} \times \text{protein\%}}{100 \times 4}
\text{fat g} = \dfrac{\text{calories} \times \text{fat\%}}{100 \times 9}This calculator splits a daily calorie target into carbohydrate, protein, and fat gram targets using your chosen percentage split. Each macronutrient has a fixed energy density: carbohydrate and protein each provide 4 kilocalories per gram, and fat provides 9 kilocalories per gram (the standard Atwater general factors used throughout nutrition science). The calculator multiplies your daily calories by each macro's percentage to get that macro's calorie share, then divides by its kcal-per-gram value to get grams. Carbohydrate, protein, and fat percentages must add up to exactly 100% — this tool does not silently rescale a split that doesn't total 100%, since doing so would silently change the diet you asked for. This is an estimate for general informational and educational purposes, based on a published formula — it is not a medical diagnosis, and it is not a substitute for individualized advice from a qualified healthcare provider. This is an energy-distribution estimate, not an individualized nutrition prescription — it does not account for micronutrient needs, medical conditions, or training-specific protein/carb timing.
Worked Examples
2,000 kcal, 40% carb / 30% protein / 30% fat
- Carb calories: 2000 × 40 / 100 = 800 kcal → 800 / 4 = 200 g carbohydrate
- Protein calories: 2000 × 30 / 100 = 600 kcal → 600 / 4 = 150 g protein
- Fat calories: 2000 × 30 / 100 = 600 kcal → 600 / 9 ≈ 66.67 g fat
- Check: 800 + 600 + 600 = 2000 kcal, matching the daily target
Frequently Asked Questions
Why do the percentages have to add up to exactly 100%?
If your carb/protein/fat percentages summed to, say, 90%, silently stretching them to fill the remaining 10% would change the diet split you actually asked for without telling you. This calculator requires an exact 100% total and tells you to adjust your inputs instead of guessing what you meant.
Why is fat's kcal-per-gram different from carbs and protein?
Carbohydrate and protein each provide about 4 kilocalories per gram, while fat is denser at about 9 kilocalories per gram. These are the standard Atwater general energy factors used throughout nutrition science and food labeling.
How do I pick my daily calorie target?
This calculator does not derive a calorie target for you — it splits whatever target you enter. If you want a number based on your maintenance calories or a weight-loss/gain goal, use the Calorie Calculator first, then enter its result here.
Can I set a macro percentage to 0%?
Yes. A 0% entry for any single macro (for example, a very low-carbohydrate split) is valid as long as the three percentages still add up to 100%.