A calorie target tells you how much to eat; macros tell you what those calories are made of. The split matters most for protein — get that right and the rest is flexible.
Don't start with percentages. Set the two macros that have a floor first — protein and fat — then let carbohydrate fill whatever calories remain. This guarantees you hit the targets that actually matter and treats carbs as the adjustable energy source they are.
Protein protects muscle (especially in a deficit) and is the most satiating macro. A common, evidence-aligned target is roughly 1.6–2.2 g per kg of body weight — our calculator uses about 1.8 g/kg as a sensible default. At 4 calories per gram, that's your first slice of the budget. More detail in how much protein per kg.
Fat supports hormones and absorption of fat-soluble vitamins, so it has a floor too — commonly around 0.6–1.0 g per kg of body weight (about 0.8 g/kg as a default). At 9 calories per gram, fat is calorie-dense, so a little goes a long way on the budget.
Whatever calories are left after protein and fat become carbohydrate, at 4 calories per gram. Carbs fuel training and daily energy; if you train hard you'll want more of your remaining budget here. There's no single "correct" carb number — it's the flexible remainder.
The calculator computes this split from your target automatically using those defaults, and the reverse meal macro decoder turns the resulting protein/carb/fat targets into actual grams of food. Remember the split is a guide, not a prescription — total calories drive weight change; macros shape body composition and how you feel.
Set protein first (about 1.6–2.2 g/kg body weight), then fat (about 0.6–1.0 g/kg), then let carbohydrate fill the remaining calories. Protein is 4 cal/g, carbs 4, fat 9.
Less than the absolute protein target. Set protein and fat by body weight, fill the rest with carbs. Total calories drive weight change; macros mainly affect body composition and satiety.