Calorie & Macro Calculator
Calculate your daily calorie needs (Mifflin-St Jeor BMR plus activity) and a protein, carbohydrate and fat split tuned to your training load and goal.
The BMR equation uses a different constant for each; it’s the only place this matters.
How this is worked out
Resting metabolism uses the Mifflin-St Jeor equation, which predicts modern body composition better than the older Harris-Benedict. Multiplying by an activity factor gives total daily energy expenditure; your goal then shifts that up or down.
Protein is set per kilogram of bodyweight by training emphasis, and rises by 0.4 g/kg in a deficit — that extra is what protects lean mass when calories are short. Carbohydrate scales with training load, because it is the fuel that actually limits endurance work. Fat takes the remaining calories, with a floor of 0.6 g/kg for hormonal health and fat-soluble vitamin absorption; if the numbers collide, carbohydrate gives way rather than protein.
Every equation here is a population average. Individual metabolic rate varies by roughly ±10%, so use the trend on the scales over a fortnight to correct the estimate.
Information only — not medical advice. These are estimates from population-level formulas, not a substitute for professional assessment. See our full disclaimer.