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Calorie & Macro Calculator

How this is calculated

Calories at rest come from the Mifflin-St Jeor equation, which is the one most dietitians reach for: ten times your weight in kilograms, plus 6.25 times your height in centimetres, minus five times your age, then plus 5 for men or minus 161 for women. That number is multiplied by an activity factor between 1.2 and 1.9 to get what you burn across a whole day.

From there the goal decides the target. Losing fat subtracts 20 percent, holding weight changes nothing, gaining muscle adds 10 percent. The split is deliberately asymmetric: a smaller surplus than deficit, because weight added quickly is rarely the weight you wanted.

Protein is set per kilogram of bodyweight rather than as a share of calories — 2.2 g when cutting, 2.0 g at maintenance, 1.8 g when gaining. Protein needs track your body, not your plate, and the requirement goes up in a deficit rather than down. Fat takes a quarter of the calories, which keeps it high enough not to cause problems, and carbohydrate gets whatever is left.

Every one of these numbers is an estimate, not a measurement. The equation was fitted to a population, and individuals sit either side of it by a few hundred calories. Use the figure as a starting point, keep your intake and your weight in the same place for two or three weeks, and adjust based on what actually happened. The scale is the measurement; this is the guess that gets you close enough to start.

This is not medical advice and not a diagnosis. If you are pregnant, have a metabolic, kidney or eating disorder, or are managing a medical condition, the right calorie and protein numbers for you come from a doctor or a registered dietitian, not from a web page.

Source: Mifflin MD, St Jeor ST, et al. (1990), American Journal of Clinical Nutrition.