What this calculates
Enter your sex, age, height, weight and how active you are, and this works out your daily calorie needs — your total daily energy expenditure, or TDEE — and how much to eat to lose about 0.25 or 0.5 kg a week, or to gain about 0.5 kg a week.
The formula
BMR (Mifflin-St Jeor)
men 10 × kg + 6.25 × cm − 5 × age + 5 · women 10 × kg + 6.25 × cm − 5 × age − 161
Daily needs (TDEE)
BMR × activity factorWeight targets
TDEE − 500 (lose about 0.5 kg a week), − 250 (lose about 0.25 kg), + 500 (gain about 0.5 kg)
The activity factors are 1.2 (sedentary), 1.375 (lightly active), 1.55 (moderately active), 1.725 (very active) and 1.9 (extra active).
Worked example
A sedentary woman of 25, 160 cm and 55 kg has a BMR of 1,264 kcal and needs about 1,264 × 1.2 = 1,517 kcal a day to keep her weight.
When to use it, and the mistakes to avoid
Use it to set a daily calorie target for losing, keeping or gaining weight, to plan meals, or to check whether an app's target is sensible.
The mistakes that cost the most:
- Overstating your activity. An hour in the gym three times a week does not make a desk job "very active". Start lower and adjust.
- Cutting too hard. A 1,000 kcal deficit loses muscle as well as fat and is hard to keep up; 250–500 is a steadier pace.
- Treating the number as exact. It is an estimate. Your weight over a few weeks is the real test.
- Not recalculating. As you lose weight your needs fall — redo it every 5 kg or so.
- Forgetting drinks and snacks. They count, and they are the easiest calories to miss.
FAQ
How many calories do I need a day?
It depends on your size, age, sex and how active you are. A moderately active man of 30, 175 cm and 70 kg needs about 2,556 kcal a day to keep his weight; a sedentary woman of 25, 160 cm and 55 kg about 1,517. Enter your own details for your figure.
What is TDEE?
Total daily energy expenditure: everything you burn in a day - your basal metabolic rate, plus moving, exercising and digesting food. It is your maintenance calories: eat this much and your weight stays about the same.
How many calories should I eat to lose weight?
Roughly 500 kcal a day less than your TDEE to lose about 0.5 kg (1 lb) a week, or 250 less for about 0.25 kg. About 7,700 kcal is a kilogram of body fat, so 500 a day for a week is 3,500 - close to half a kilogram.
Which activity level should I pick?
Be honest and lean lower: most people overestimate. A desk job with a few walks is sedentary (1.2). Exercise 1-3 days a week is lightly active (1.375); 3-5 days moderately active (1.55); hard exercise 6-7 days very active (1.725); and a physical job or training twice a day extra active (1.9).
What is the lowest I should eat?
Health services generally advise not going below about 1,200 kcal a day for women or 1,500 for men without medical supervision. If your weight-loss target falls below that, the calculator warns you - lose weight more slowly, or add activity instead.
Why am I not losing weight on these numbers?
The equations are averages, and any one person can differ by 10% or more. Food is also easy to under-count. Weigh yourself regularly for two or three weeks and adjust by 100-200 kcal a day if the trend is not what you expect.