How to calculate macros

Calculating macros means turning a calorie target into daily gram targets for protein, carbohydrates, and fat. It's two steps: find your calorie target, then split it by your chosen diet style. The math is short and consistent across every calculator on this site.

Step 1 — Estimate calorie needs (BMR and TDEE)

Your Basal Metabolic Rate (BMR) is the energy needed to keep you alive at rest. The Mifflin–St Jeor equation estimates it:

• Men: 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
• Women: 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Multiply BMR by an activity factor to get Total Daily Energy Expenditure (TDEE): sedentary 1.2, light 1.375, moderate 1.55, active 1.725, very active 1.9. Adjust for goal — about −500 kcal/day for fat loss, +250–500 kcal/day for muscle gain — to get your daily calorie target.

Step 2 — Split by macro percentages

Apply a diet-style percentage split to that calorie target, then convert calories back to grams. Protein and carbs are 4 kcal per gram, fat is 9 kcal per gram:

• grams of protein = (calories × protein%) ÷ 4
• grams of fat = (calories × fat%) ÷ 9
• grams of carbs = (calories × carbs%) ÷ 4

For example, 2,400 kcal on a balanced 30/40/30 split becomes 180 g protein, 240 g carbs, and 80 g fat. On keto (25/5/70) the same calories yield 150 g protein, 187 g fat, and carbs fill the remaining calories at about 29 g.

Why splits vary by goal

The split shifts where energy comes from, while the calorie target determines weight change. Cutting usually pairs the deficit with higher protein to protect lean mass. Bulking keeps protein high and lets carbs absorb most of the surplus to fuel training. Keto deliberately drives fat up and carbs down to sustain ketosis. None of these is universally best — the split should fit your food preferences and consistency.

Standalone protein targets

If you only care about protein, you can skip the full macro flow and use bodyweight rules of thumb: 0.7–1 g/lb for general fitness, up to 1–1.2 g/lb for muscle gain. That's what the protein calculator returns.

Putting it together

The two-step math is why all four calculator pages here share one calculation engine — only the presets (goal and diet style) and the surrounding copy change. Try the main macro calculator to see grams computed live for your numbers.

These are general estimates. They are not medical or nutritional advice. Consult a registered dietitian or doctor before making significant diet changes.