Calorie Calculator

Your daily calorie needs from the Mifflin-St Jeor equation — BMR, maintenance calories, and targets for losing or gaining weight.

How the calculation works

The calculator uses the Mifflin-St Jeor equation, the formula most dietitians rely on: BMR = 10×weight + 6.25×height − 5×age (+5 for men, −161 for women). That's what your body burns at complete rest. Multiplying by an activity factor gives your TDEE — maintenance calories. Eat roughly 500 kcal under maintenance to lose about 0.5 kg per week, or 300–500 over to gain lean weight gradually. Height in feet? Convert with the Unit Converter first.

BMR and TDEE explained

Your BMR (basal metabolic rate) is the energy your body uses at complete rest just to stay alive — breathing, circulation, cell repair. Your TDEE (total daily energy expenditure) is your BMR multiplied by an activity factor to include movement and exercise. TDEE is the number that actually matters for weight goals: eat below it to lose, above it to gain.

Losing or gaining weight safely

Roughly 7,700 calories equals one kilogram of body fat, so a daily deficit of about 500 calories loses around 0.5 kg per week — a safe, sustainable pace. Avoid very low intakes: eating below your BMR for long periods slows metabolism and loses muscle. To gain lean weight, add 300–500 calories a day alongside strength training.

Choosing your activity level honestly

The activity multiplier moves your daily target more than almost anything else, and it is where most people overestimate. The standard bands are sedentary ×1.2 (desk work, little deliberate exercise), lightly active ×1.375 (1–3 sessions a week), moderately active ×1.55 (3–5 sessions), very active ×1.725 (6–7 sessions) and extra active ×1.9 (physical job plus training).

On a BMR of 1,600, sedentary gives 1,920 calories while very active gives 2,760 — a gap of over 800 calories a day. Choosing a band too generous is the single most common reason a "calorie deficit" quietly stops working. A useful check: if your job is seated and you train three times a week, you are lightly to moderately active, not very active. Gym sessions matter less than people expect; the bigger driver is how much you move during the other twenty-three hours.

Setting a realistic deficit or surplus

Roughly 7,700 calories equals a kilogram of body fat, so a daily deficit of 500 predicts about half a kilo a week. That rate is sustainable for most people and preserves muscle. Larger deficits get diminishing returns: below about 1,200 calories for women or 1,500 for men, you risk losing muscle alongside fat, and adherence collapses.

For gaining, a 250–500 surplus paired with strength training is enough. Bigger surpluses mostly add fat, not muscle — the body can only build so fast regardless of intake.

Expect the arithmetic to drift over time. As you lose weight your BMR falls (a smaller body costs less to run), so a deficit that worked at the start becomes maintenance later. Recalculate every 4–5 kg rather than assuming one number holds forever.

Why the scale lies day to day

Body weight swings by one to two kilos for reasons unrelated to fat. Sodium and carbohydrate intake shift water retention, glycogen stores hold roughly 3 g of water per gram, digestion means undigested food is sitting in you, and hormonal cycles add their own fluctuation.

The practical answer is to weigh under the same conditions — morning, after the bathroom, before eating — and judge the weekly average rather than any single reading. A week where the average drops 0.4 kg is working, even if two individual days went up.

Frequently asked questions