How are macros calculated?

Macronutrients — protein, carbohydrates, and fat — each contribute a fixed number of calories per gram: protein and carbs provide 4 kcal/g; fat provides 9 kcal/g. To calculate your macros, we first set protein and fat in grams based on your goal and body weight, then fill remaining calories with carbohydrates.

Protein is prioritized because it’s the most important macro for body composition — it preserves muscle during a cut, drives muscle protein synthesis during a bulk, and is the most satiating macronutrient per calorie.

Fat is set as a percentage of total calories (minimum ~20%) to support hormone production and fat-soluble vitamin absorption. Carbohydrates fill the remaining calories and fuel training performance.

How macros are calculated, in order

There is a correct sequence to setting macronutrients, and following it removes most of the confusion. Calories come first because they determine weight change. Protein comes second because it is the macro with a genuine target. Fat comes third because it has a floor. Carbohydrate is whatever is left.

Step 1 — total calories

Start from your TDEE, then apply your goal. Fat loss is 15 to 25 percent below; a lean bulk is 5 to 10 percent above; maintenance is TDEE itself. Every gram figure below is derived from this number, so getting it approximately right matters more than any macro split.

Step 2 — protein, set from bodyweight

Protein has the strongest evidence base of the three. The 2018 meta-analysis by Morton and colleagues, pooling 49 trials, found benefits to lean mass from resistance training rising up to approximately 1.6 g per kilogram of bodyweight per day, with no reliable further gain beyond that. Requirements rise in a deficit, because amino acids are diverted to fuel and muscle protein synthesis is blunted.

At 4 calories per gram, a 75 kg person at 2.0 g/kg eats 150 g of protein — 600 calories. Our protein target table converts every target into total grams for 15 bodyweights, and the full reasoning is in how much protein you actually need.

Step 3 — fat, which has a floor not a target

Dietary fat is required for hormone production, the absorption of vitamins A, D, E and K, and cell membrane structure. Below roughly 0.5 g per kilogram of bodyweight — or about 20 percent of calories — those functions start to suffer, and very low fat diets have been associated with reduced testosterone in men. Set 20 to 35 percent of calories, toward the lower end when cutting to leave room for carbohydrate.

Step 4 — carbohydrate as the remainder

Carbohydrate is the only macro with no strict requirement, which is why it goes last — and also why it is the most useful lever. It fuels training, refills glycogen, and for most people makes a diet feel survivable.

A full worked example

An 80 kg man with a TDEE of 2,700 who wants to lose fat at a moderate rate.

That is 160 g protein, 60 g fat, 245 g carbohydrate — roughly 30 / 25 / 45 percent by calories. Note that the percentages were an output, not an input. Starting from a percentage split rather than a protein target is the most common way people end up under-eating protein.

How precise do you need to be?

• Calories: within about 100 a day. This is the number that determines weight change.
• Protein: within about 15 g. Hitting it most days beats hitting it exactly on some.
• Fat and carbs: considerably looser. Provided fat stays above its floor, trading between them has little effect on body composition and a large effect on how you feel. Prefer carbohydrate if you train hard; prefer fat if it keeps you fuller.

Meal timing and distribution are second-order. Each feeding stimulates muscle protein synthesis up to roughly 0.4 g/kg, so three to five protein-containing meals is a better pattern than one enormous one — but total daily intake dominates. If you are new to this, our beginner walkthrough goes through the whole process at a slower pace.