Calorie Calculator

How this calorie calculator works

This tool estimates your Total Daily Energy Expenditure (TDEE) using the Mifflin-St Jeor equation, widely regarded by dietitians as more accurate than older formulas like Harris-Benedict. It first calculates your Basal Metabolic Rate (BMR) — the energy your body burns at complete rest just to keep organs functioning — then multiplies it by an activity factor that reflects how much you move in a typical week.

For men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. For women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. The activity multipliers range from 1.2 for a mostly sedentary lifestyle up to 1.9 for athletes training twice a day. Multiplying BMR by that factor gives your maintenance calories — the number you'd eat to keep your current weight stable.

From there, the calculator applies the common rule of thumb that one kilogram of body fat stores roughly 7,700 kcal, so a daily deficit of about 500 kcal produces close to 0.5 kg of loss per week, and 1,000 kcal roughly 1 kg per week. The same logic applies in reverse for weight gain. Keep in mind these are estimates: individual metabolism, muscle mass, sleep, stress, and medication can all shift real-world results. Re-check the numbers every few weeks as your weight changes, since your maintenance calories shift along with it, and avoid extreme deficits for long periods without guidance from a doctor or dietitian.

Frequently asked questions

Should I eat exactly the number this calculator gives me? Treat it as a starting point rather than an exact target. Track your actual weight change over 2–3 weeks and adjust up or down by 100–200 kcal if the trend doesn't match your goal.

Why do two people with the same stats get different maintenance calories? The activity multiplier does most of the work here — someone training six days a week burns meaningfully more than someone with a desk job and no exercise, even at identical height and weight.

Is a 500 kcal deficit always the right amount? It's a common, moderate starting point for roughly 0.5 kg of weekly loss, but smaller deficits are usually more sustainable long-term, especially for people who don't have much weight to lose.

Worked example

A 30-year-old woman, 165 cm, 65 kg, moderately active: BMR = 10(65) + 6.25(165) − 5(30) − 161 = 1370.25 kcal. Multiplied by the moderate-activity factor of 1.55 gives roughly 2,124 kcal/day to maintain weight, and about 1,624 kcal/day for a 500-kcal deficit.

Should I recalculate as I lose weight? Yes — every 4–5 kg lost lowers your BMR, so maintenance calories drop too. Re-run the calculator every few weeks rather than eating the same fixed number for months.

Does this calculator account for muscle mass? Not directly. Two people at the same weight but different muscle-to-fat ratios burn slightly different amounts at rest; the Mifflin-St Jeor formula is a population average, so treat the result as a starting estimate.