Macro Calculator

Turning a calorie target into protein, carbs and fat

"Macros" are the three energy-providing nutrients: protein, carbohydrate and fat. Each has a roughly fixed energy density — the Atwater factors of 4, 4 and 9 kilocalories per gram. Once you know how many calories you want per day and what percentage should come from each macro, converting to grams is arithmetic: multiply calories by the percentage, divide by that macro’s calories-per-gram.

Calories decide whether weight goes up or down; macros shape what happens within that calorie level. Adequate protein preserves muscle when you are in a deficit and supports recovery from training. Carbohydrate fuels higher-intensity exercise and is the easiest lever to move up or down. Dietary fat supports hormone production and satiety, with a common floor around 0.5–0.8 g per kg of body weight.

The presets here cover the usual starting points: balanced (about 30/40/30), high-protein (40/40/20), low-carb (40/20/40) and keto (25/5/70). None is magic. Adherence beats theoretical optimality, so pick the split that fits how you like to eat and train. A widely used method is to set protein first at 1.6–2.2 g per kg of body weight, then divide the remaining calories between carbs and fat by preference.

Treat the output as a target range, not a prescription. Day-to-day variation is normal and fine; the weekly average is what matters. Food quality, fibre, micronutrients, sleep and training consistency all influence results and are not captured by a macro ratio. This is a general fitness tool — therapeutic diets for medical conditions must come from a qualified dietitian or physician.

All calculations run in your browser. Nothing you enter is stored or sent anywhere.

kcal from macro   = calorieTarget × (macro% ÷ 100)
grams of protein  = kcalₚ ÷ 4
grams of carbs    = kcal_c ÷ 4
grams of fat      = kcal_f ÷ 9
(custom percentages are normalised so protein% + carb% + fat% = 100)

Worked examples

• 2,000 kcal, balanced 30/40/30: about 150 g protein, 200 g carbohydrate and 67 g fat.
• 2,000 kcal, keto 25/5/70: about 125 g protein, 25 g carbohydrate and 156 g fat.
• 2,400 kcal, high-protein 40/40/20: about 240 g protein, 240 g carbohydrate and 53 g fat.

A custom split that does not add up to 100% is scaled proportionally, so the grams always add back up to your calorie target.

A protein-first approach

Many dietitians set protein from body weight rather than as a percentage, then split the remaining calories. For a 75 kg person aiming for 1.8 g/kg, that is 135 g of protein, or 540 kcal. On a 2,200-kcal target that leaves 1,660 kcal; giving 30% of total calories to fat (660 kcal, about 73 g) leaves about 250 g of carbohydrate. Enter the resulting percentages as a custom split to see them side by side with the presets.

Tracking in practice

• Hit protein and total calories most days; carbohydrate and fat can trade off against each other without much effect on results.
• Weigh foods for a week or two to calibrate your eye — portion estimates are usually the biggest error in food logging.
• Alcohol provides 7 kcal per gram and counts toward calories but none of the three macros.
• For diabetes, kidney disease or a medically supervised ketogenic diet, macro targets should come from a doctor or registered dietitian.