Macros for Weight Loss: How to Set Protein, Carbs, and Fat

Macros for weight loss start from a calorie target set below your maintenance needs, then divide those calories among protein, carbohydrate, and fat. To turn a percentage split into gram targets, the rule is grams = calories × percent ÷ kcal-per-gram, using 4 for protein and carbs and 9 for fat. Protein is held high on a cut.

This is general information, not personalised dietary advice. To turn a calorie target into gram targets without arithmetic, use the macro calculator.

Start from a calorie target, not the macros

Macros sit downstream of calories, so the first decision is how many calories you eat in a day. Fat loss happens when intake runs below the energy you burn, which is your total daily energy expenditure. Estimate that figure with the TDEE calculator, then subtract a moderate deficit to get the target you will actually split. The macros only describe how that fixed pool of energy is shared out, so the calorie number has to come first.

Convert a split to grams with the Atwater factors

Each macro carries a known amount of energy per gram. These are the Atwater factors, and they are the bridge between a percentage split and a plate of food. Protein and carbohydrate release the same energy per gram, while fat is the most energy-dense of the three. To find the grams of any macro, take that macro's slice of the calories and divide by its energy factor.

The conversion is the same every time. Multiply the calorie target by the macro's percentage, then divide by that macro's kcal-per-gram value to land on grams.

Keep protein high while cutting

Protein does the most work on a cut, so it gets the largest or joint-largest share. Eating in a deficit puts lean muscle at risk, and a high protein intake helps preserve it while you lose fat. Protein is also the most filling macro per calorie, which makes the deficit easier to hold. A common target when losing fat while keeping muscle is set per kilogram of bodyweight rather than as a flat percentage, and the protein calculator works it out directly.

Fat needs a floor, and carbs fill the rest. Dietary fat supports hormone production and the absorption of some vitamins, so the split should not drop it too low. Once protein is set high and fat clears a sensible floor, carbohydrate takes whatever calories remain, fuelling training and daily activity. The presets in the macro calculator each balance these three priorities differently.

A worked split for fat loss

The high-protein split suits a cut, so work one through. Take a fat-loss calorie target and apply the high-protein preset, which puts protein and carbohydrate level at the top and keeps fat lean but above a floor. Convert each percentage to grams with the Atwater factors from above. Carbohydrate and protein land on the same gram figure here because they share both the same percentage and the same energy factor, while fat works out lower despite a smaller slice because it packs more energy per gram.

Those three gram targets are what you carry to a food tracker. The percentages set the shape of the diet, and the grams make it something you can measure on a plate.

Quick reference

Set the calorie target first, hold protein high, give fat a floor, and let carbs fill the rest, then convert each share to grams with the Atwater factors. To skip the arithmetic, enter your calorie target and split into the macro calculator and it returns protein, carbohydrate, and fat in grams.