Calorie calculator

How daily calorie needs are calculated

BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + s (s = +5 for men, −161 for women)

Your basal metabolic rate (BMR) is the energy your body uses at complete rest — for breathing, heartbeat, body temperature and tissue repair. It is the basis of every calorie calculation, and this calculator estimates it with the Mifflin-St Jeor equation, published in 1990 and today the most widely used in clinical practice. The authors publish the rounded form (10 / 6.25 / 5) in that same paper; it differs from the original regression by a fraction of a percent.

Example: a man, 30 years old, 180 cm, 80 kg. BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal per day. That is what he would burn lying down all day with no activity at all.

Activity coefficients

Daily calories (TDEE) = BMR × activity coefficient

Actual daily expenditure (TDEE) is your BMR multiplied by an activity coefficient. The calculator offers the five conventional levels: 1.2 — sedentary, little or no exercise; 1.375 — lightly active, 1–3 days of exercise per week; 1.55 — moderately active, 3–5 days per week; 1.725 — very active, 6–7 days per week; 1.9 — extra active, a physical job or two workouts a day.

Continuing the example: 1,780 kcal × 1.55 (moderately active) = 2,759 kcal per day to maintain weight. To lose weight you subtract 500 kcal from that, to gain weight you add 500 kcal.

An important note on provenance: these five coefficients are a convention from fitness and clinical practice — they have no published primary source and are not a figure from the World Health Organization or the FAO. FAO/WHO/UNU's human energy requirements report (2004) publishes its own scale of PAL values (1.40–1.69 for sedentary and light activity, 1.70–1.99 for active, 2.00–2.40 for vigorously active), but PAL is a different quantity: total expenditure divided by BMR across the full 24 hours, including all everyday activity outside training. That is why the lowest FAO/WHO/UNU value is higher than our 1.2 coefficient.

How accurate the estimate is, and how to use it

Mifflin-St Jeor is the most reliable of the widely used equations and, for most healthy adults, lands within about ±10% of measured resting metabolic rate (Frankenfield et al., 2005). For an individual the deviation can be larger: the equation was derived mostly on white adults, and older people and people with unusual body composition are under-represented. Treat the result as a starting point and correct it against your actual weight change over a few weeks.

The rule "−500 kcal per day ≈ 0.5 kg per week" is a simplification going back to Wishnofsky (1958, about 7,700 kcal per kilogram of body weight). Real weight loss is not linear: as weight falls, so do resting metabolic rate and the energy cost of movement, so the static rule overestimates long-term loss — by up to about double in the first year, per Hall et al. (2011). Expect a slower pace than calculated and recalculate regularly with your new weight.

This calculator is informational and not medical or nutritional advice. The estimate applies to healthy adults (18+) — not to children and adolescents, pregnancy, breastfeeding, people under medical treatment, or elite athletes with unusual body composition. Consult a doctor or dietitian for a nutrition plan.