Calorie calculator: how many calories do you need a day?

First the calculator estimates the energy your body uses at rest, with the Mifflin-St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, then + 5 for men or − 161 for women. Studies found it closer to measured values than older equations for most people.

It then multiplies that resting energy by your activity level: 1.2 with little or no exercise, up to 1.9 with very hard exercise or a physical job. The result is the number of calories that keeps your weight stable.

To lose about 0.5 kg (1 lb) a week, you eat about 500 calories less a day; to lose 0.25 kg (½ lb), about 250 less. The calculator never goes below 1,200 calories a day for women or 1,500 for men, because eating less needs a doctor’s supervision.

Treat it as a starting point. Every body is different, so weigh yourself once a week for 3 to 4 weeks: if your weight moves the wrong way, change your daily calories by 100 to 200 and check again.

Where the calories come from matters as much as how many there are. Drinks and foods high in sugar, saturated fat and salt add calories quickly without filling you up, which is why the result also shows your daily limits for them.