What is the Macronutrient Split Calculator?
This tool converts your total daily calorie target and a chosen macronutrient ratio into the actual number of grams of protein, carbohydrate, and fat to eat each day. It works for any goal — cutting, maintenance, or bulking — because it simply translates the percentages you choose into grams.
How to use it
Enter your daily calorie goal, then the percentage of those calories you want from protein, carbs, and fat. The three percentages should add up to 100%. The calculator returns the calories and grams for each macro.
The formula explained
Each macronutrient has a fixed energy density: protein and carbohydrate provide about 4 kcal per gram, while fat provides about 9 kcal per gram. First we find each macro's calorie share (calories × percent ÷ 100), then divide by its kcal-per-gram value to get grams.
$$\begin{gathered} \text{Protein (g)} = \frac{\text{Calories} \times \dfrac{\text{Protein \%}}{100}}{4} \\[1.5em] \text{Carbs (g)} = \frac{\text{Calories} \times \dfrac{\text{Carb \%}}{100}}{4} \\[1.5em] \text{Fat (g)} = \frac{\text{Calories} \times \dfrac{\text{Fat \%}}{100}}{9} \end{gathered}$$
Worked example
For a 2,000 kcal diet at 30% protein, 40% carbs, 30% fat: protein = $$2000 \times 0.30 = 600 \text{ kcal} \div 4 = 150 \text{ g}$$ carbs = $$2000 \times 0.40 = 800 \text{ kcal} \div 4 = 200 \text{ g}$$ fat = $$2000 \times 0.30 = 600 \text{ kcal} \div 9 \approx 66.7 \text{ g}$$
FAQ
Why does fat use 9 instead of 4? Dietary fat is more energy-dense, supplying roughly 9 kcal per gram versus 4 kcal per gram for protein and carbs.
Do my percentages have to total 100%? Yes, for an accurate split. If they don't, the calculator flags it but still computes grams from your numbers.
What's a common ratio? A balanced starting point is 30/40/30 (protein/carbs/fat), but adjust to your training, preferences, and goals.
