Macro Calculator — Protein, Carb & Fat Grams From Calories

Quick answer: Protein and carbs carry 4 kcal per gram, fat carries 9. A 2,400 kcal day split 30/40/30 is 180 g protein, 240 g carbs, 80 g fat — the percentages are the input, the grams are what you actually eat.

The rule

Protein g = (calories × P%) ÷ 4
Carb g = (calories × C%) ÷ 4
Fat g = (calories × F%) ÷ 9

Worked example — 2,400 kcal, 30% protein / 40% carbs / 30% fat: protein 2,400 × 0.30 ÷ 4 = 180 g; carbs 2,400 × 0.40 ÷ 4 = 240 g; fat 2,400 × 0.30 ÷ 9 = 80 g. Check: 180×4 + 240×4 + 80×9 = 720 + 960 + 720 = 2,400 ✓.

Common splits and what they emphasize

Split (P/C/F)	2,400 kcal → grams	Character
30/40/30	180 / 240 / 80	Balanced default
35/20/45	210 / 120 / 120	Lower-carb
20/5/75	120 / 30 / 200	Keto-style

Sanity checks before trusting a split

Protein below ~1.2 g/kg of body weight under-supports muscle retention on a deficit; fat below ~0.5 g/kg can affect hormone function over long stretches; carbs fueling hard training below ~3 g/kg makes heavy sessions feel flat. If a fashionable split violates these bands for your body weight, treat it skeptically. Set your calorie target first (see the TDEE guide), then split it — the TDEE & Macro Calculator does both steps; Macro Split and Daily Protein Need cover the individual pieces.

This is arithmetic, not a diet prescription. Medical conditions, pregnancy and eating-disorder history all change appropriate targets — use professionals for those conversations.

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Frequently asked questions

How do I calculate macros from calories?

Assign percentages to protein, carbs and fat, then divide: protein and carb grams = (calories × share) ÷ 4; fat grams = (calories × share) ÷ 9. Example: 2,400 kcal at 30/40/30 → 180 g protein, 240 g carbs, 80 g fat.

What is the 4-4-9 rule?

The energy densities: 4 kcal per gram of protein, 4 per gram of carbohydrate, 9 per gram of fat. It is how nutrition labels convert grams to calories and how macro percentages become gram targets.

What macro split should I use?

Start from a balanced 30/40/30 and adjust one variable at a time against your training and appetite. Keep protein at 1.2–2.2 g/kg body weight and fat above 0.5 g/kg regardless of style.

Do macro grams or percentages matter more?

Percentages are the input; grams are the actionable output. Nobody weighs "30%" — you weigh 180 g of protein. Always convert the split into gram targets for your calorie level.

Macros: Calories → Grams With the 4-4-9 Rule