Macro math has one lookup table: protein and carbs cost 4 calories a gram, fat costs 9. Everything else is arithmetic. On 2,400 calories, a 40/30/30 split is exactly 240g carbs, 180g protein, and 80g fat, and the grams rebuild your total: 240×4 + 180×4 + 80×9 = 2,400. Here's how to pick the split and run the numbers yourself.
Grams = daily calories × macro share ÷ calories per gram. That's it. The only mistakes people make are using 9 for carbs (it's fat's number), forgetting the percent has to be a decimal, and letting rounding drift so the grams no longer sum to the calorie target. Do the rebuild check every time you change something: protein×4 + carbs×4 + fat×9 should land within about 20 calories of your target. If it doesn't, an input is wrong.
| Goal | Split (C/P/F) | Why it works |
|---|---|---|
| General health | 45 / 25 / 30 | Closest to a normal diet; sits mid-AMDR |
| Recomposition, Zone-style | 40 / 30 / 30 | Enough protein to hold muscle without crowding out carbs |
| Fat loss with training | 35 / 35 / 30 | High protein protects muscle and kills hunger in a deficit |
| Aggressive cut | 30 / 40 / 30 | Protein maxed when calories are low |
| Low-carb lifestyle | 20 / 40 / 40 | Satiety and steady glucose; still above keto |
| Ketogenic | 10 / 25 / 65 | Outside the AMDR; therapeutic tool, not a default |
Two of those rows deserve a caveat. The National Academies set Acceptable Macronutrient Distribution Ranges of 10–35% protein, 45–65% carbs, and 20–35% fat; the low-carb and keto rows deliberately leave those bands, which is a choice to make with a reason (and for keto, ideally a clinician's nod). Everything else is preference inside a healthy envelope.
Percentage splits quietly let protein shrink when calories drop, which is exactly backwards for a dieter. The fix is to anchor protein in grams first: 0.7 to 1.0 g per pound of body weight (the evidence-based band for muscle is 1.4–2.0 g per kg, and returns flatten past about 1 g/lb). Then set fat as a percentage, usually 25–35%, and give every remaining calorie to carbs.
Worked: a 180-lb lifter cutting on 2,224 calories anchors protein at 0.8 g/lb = 144g (576 cal), sets fat at 30% = 667 cal = 74g, and feeds the rest to carbs: (2,224 − 576 − 667) ÷ 4 = 245g. Notice what happened: a "high protein" day that still carries 245g of carbohydrate for training. A fixed 30/40/30 percentage would have forced protein to 222g, more than needed, and stripped carbs to 167g.
Percentage presets or protein-anchored, with the calorie rebuild check shown every time.
Macro Split Calculator →The split is step two. Step one is the calorie number itself, and it should come from your stats, not a friend's plan. Our calorie deficit calculator gives a weight-loss target with the NIH floor check, and the calorie calculator handles maintenance and muscle-gain numbers. Once calories exist, the split falls out in thirty seconds.
Grams on a screen don't feed anybody. Divide targets across meals, 3 or 4 usually, aiming for 25 to 40g of protein per meal; muscle protein synthesis responds to per-meal doses more than to one giant dinner. Common anchors: a chicken breast or a scoop and a half of whey is roughly 30 to 40g protein; a cup of cooked rice is about 45g carbs; a tablespoon of oil or a small handful of nuts is roughly 10 to 14g fat. Weigh food for the first two weeks; after that you'll eyeball within 10%, which is plenty, because the weekly average decides outcomes.
And on precision: chasing macros to the gram daily is stress without payoff. Hitting protein daily, calories within about 100 over the week, and letting carbs and fat slosh between days produces the same results with half the misery. Rest-day carb cuts of 50–100g, higher carbs before hard sessions, same protein always, is the pattern trained people converge on.
Take your daily calories, multiply by the share each macro gets, and divide by that macro's calories per gram: 4 for protein, 4 for carbs, 9 for fat. On 2,400 calories, 30% protein is 2,400 × 0.30 = 720 calories ÷ 4 = 180g. Do all three and the grams should rebuild your calorie total, which is the built-in error check.
Most land between 40/40/20 and 30/40/30 carbs/protein/fat in a growth phase, with protein anchored near 0.8 to 1 g per pound and carbs feeding training. In a contest-prep cut, protein rises (35–40% or 1 g/lb), fat holds at 20–30% for hormones, and carbs absorb the reduction. The constant across phases is protein; carbs and fat trade places.
They're the same budget at different zoom levels: your macros always sum to your calories. Counting macros wins because protein and fiber change body composition and satiety in ways a plain calorie number hides. Two identical 2,200-calorie days feel very different when one carries 160g of protein and the other 80g.
Yes. The idea that mixing fat and carbs in one meal causes unique fat gain has no good evidence behind it; total energy balance over the day and week is what matters. Food quality and protein per meal matter more than food-combining rules that mostly make eating harder.