Guide
How BMR and Daily Calorie Needs Are Calculated
Learn what BMR is, the Mifflin-St Jeor formula, and how activity level sets your daily calorie needs.
A BMR (basal metabolic rate) calculator estimates the calories your body burns at complete rest, then applies an activity factor to estimate your daily maintenance calories. It is the starting point for any weight-change plan.
What BMR is
BMR is the energy your body uses just to stay alive — breathing, circulating blood, keeping cells working — while at rest. It is the largest component of most people's daily energy expenditure. Total daily energy expenditure (TDEE) is BMR multiplied by an activity factor.
The Mifflin-St Jeor formula
Men: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5
Women: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age − 161
Mifflin-St Jeor is the most widely recommended modern formula. The older Harris-Benedict formula is also available and gives slightly higher estimates.
Activity factors
- Sedentary (little/no exercise): ×1.2
- Lightly active (1–3 days/week): ×1.375
- Moderately active (3–5 days/week): ×1.55
- Very active (6–7 days/week): ×1.725
- Extra active (physical job + training): ×1.9
How to use the calculator
- Enter age, sex, height, and weight.
- Choose your activity level.
- Read your BMR and estimated daily calories.
Examples
A 30-year-old woman, 165 cm, 65 kg, lightly active: BMR ≈ 1383 kcal; TDEE ≈ 1383 × 1.375 ≈ 1902 kcal. To lose weight slowly, she might aim for about 1,400–1,600 kcal/day; to gain, about 2,100–2,200.
When a BMR calculator is useful
- Setting a calorie target for weight loss, maintenance, or gain.
- Understanding how many calories you burn at rest.
- Comparing estimated needs before changing diet or activity.
- Planning nutrition for fitness goals.
Put it into practice
Use the Calorie / BMR Calculator right now — free, in your browser, no sign-up required.
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