Calorie calculator

How it's calculated

First comes resting energy expenditure, the energy your body burns at rest. It uses the Mifflin-St Jeor equation, which is more accurate than the older Harris-Benedict formula for people today and is now the standard.

For men: 10 × weight in kg + 6.25 × height in cm − 5 × age + 5. For women it's the same, but subtract 161 at the end.

Then resting energy is multiplied by a daily activity factor, from 1.4 for a desk job to 1.8 for physical work. Workouts aren't included in this factor: the app has a mode that adds a workout's calories to that day's target. The result is your maintenance.

Losing and gaining

For weight loss, 550 kcal a day is subtracted from maintenance, which is roughly half a kilogram a week. For gain, enough is added for your weight to grow by half a percent of body weight a week, so you gain less fat.

The target never drops below a safe minimum: 1,500 kcal for men and 1,200 for women. For a different pace, use the calorie deficit calculator.

Why the number is an estimate

Any formula gives an estimate for an average person. Your real expenditure can differ by about 10 percent either way. The honest test is to eat at the target for two or three weeks and watch your average weight. If it holds steady, you've found your maintenance.