0333 012 4065Live Chat
Sex
Height
Weight
Current weight
Goal weight

What's behind the numbers

The starting point is your Basal Metabolic Rate (BMR) — how much energy your body burns at complete rest. We estimate it with the Harris–Benedict equation from your sex, age, height and current weight, then scale it by your activity level to find your maintenance calories: the intake at which your weight holds steady.

Working back from your goal date

One kilogram of body weight corresponds to roughly 7,700 kcal. Knowing how much weight you want to change and how many weeks you've allowed, the calculator finds the daily deficit (or surplus) required, and applies it to your maintenance calories to produce your daily target.

Keeping the pace sensible

As a rule, losing more than about 1 kg a week — or dropping below roughly 1,200 kcal a day for women or 1,500 kcal for men — isn't generally recommended. Should your goal date force the plan past those limits, you'll see a warning; allowing more time is usually the better answer. Treat all of this as a general guide rather than personalised medical advice.