How it works
Daily calorie needs are basal metabolic rate multiplied by how active you are, a figure usually called TDEE (total daily energy expenditure): TDEE = BMR × activity factor.
- The calculator works out your BMR with the Mifflin–St Jeor equation.
- It multiplies by the activity factor you choose, from 1.2 for a desk job to 1.9 for hard physical work.
- Eat about that many calories to hold your weight; eat below it to lose, above it to gain.
Body fat stores roughly 7,700 kcal per kilogram (3,500 kcal per pound). A deficit of 500 kcal a day is therefore about half a kilo a week — fast enough to see progress, slow enough to keep muscle.
| Activity level | Multiplier |
|---|---|
| Sedentary — desk job, little exercise | 1.2 |
| Light — exercise 1–3 days a week | 1.375 |
| Moderate — exercise 3–5 days a week | 1.55 |
| Very active — exercise 6–7 days a week | 1.725 |
| Extra active — hard training or physical job | 1.9 |
Examples
Two people, same height, different activity:
- Woman, 30, 163 cm, 62 kg, lightly active: BMR 1328 × 1.375 = 1826 kcal to maintain, 1326 kcal to lose about 0.5 kg a week.
- Man, 35, 180 cm, 85 kg, very active: BMR 1805 × 1.725 = 3114 kcal to maintain.
Weigh yourself weekly rather than daily: water, salt and the previous day's meals move the scale far more than fat does.
These formulas are population averages published in peer-reviewed research. They cannot see your muscle mass, frame or medical history, so treat the result as a starting point and talk to a doctor or dietitian before making big changes.
Related: BMI Calculator, BMR Calculator, Bra Size Calculator.
Calorie Calculator: frequently asked questions
- How many calories should I eat a day?
- It depends on sex, age, size and activity. Typical ranges: about 1,800–2,400 kcal for adult women and 2,200–3,000 for adult men. Use the calculator for your own estimate.
- How many calories are in a kilogram of fat?
- About 7,700 kcal (roughly 3,500 kcal per pound), which is why a 500 kcal daily deficit gives about 0.5 kg loss per week.
- What is the lowest safe calorie intake?
- Without medical supervision, generally no lower than about 1,200 kcal a day for women and 1,500 for men.