Basal Metabolic Rate is the number of calories your body burns at complete rest to keep basic functions like breathing, circulation and cell repair running. It does not include any activity.

Which formula does this use?

The Mifflin-St Jeor equation, widely regarded as the most accurate predictive BMR formula for the general population. For men it is 10×kg + 6.25×cm − 5×age + 5; for women the final term is −161.

Is my data uploaded anywhere?

No. Every calculation runs entirely in your browser and nothing is sent to a server or stored.

What is the difference between BMR and TDEE?

BMR is calories burned at complete rest. TDEE is BMR multiplied by an activity factor (1.2 to 1.9) to include daily movement and exercise. BMR is always the smaller of the two and forms the base of every calorie target.

Why is BMR lower for women than men?

The Mifflin-St Jeor equation ends with +5 for men and −161 for women, a 166 kcal gap reflecting the higher average lean body mass and lower body-fat percentage in men. Muscle is more metabolically active than fat.

Does BMR decrease with age?

Yes. The formula subtracts 5 kcal for every year of age, so an otherwise identical 50-year-old has a BMR about 100 kcal lower than a 30-year-old. Loss of muscle mass over time also lowers real-world metabolism.

Is BMR the same as RMR?

Almost. Resting Metabolic Rate (RMR) is measured under slightly less strict conditions than true BMR and tends to be a few percent higher, but the two are used interchangeably for everyday calorie planning.

BMR Calculator — Gera Tools

BMR calculator — Mifflin-St Jeor

Your Basal Metabolic Rate (BMR) is the number of calories your body burns just to stay alive at complete rest — powering breathing, circulation, brain function and cell repair, with no movement at all. Knowing it is the starting point for any calorie plan: every diet or maintenance target is built on top of your BMR. This calculator uses the Mifflin-St Jeor equation, the most accurate predictive formula for the general adult population, and works in metric or imperial units.

How it works

Imperial inputs are converted to metric first (1 lb = 0.453592 kg, 1 in = 2.54 cm). The shared base term is 10 × kg + 6.25 × cm − 5 × age, then the sex constant is added:

Male: base + 5
Female: base − 161

BMR does not include any activity. To estimate your full daily needs, multiply the result by an activity factor — that is exactly what the TDEE calculator does.

Example

A 30-year-old man, 178 cm and 75 kg:

BMR = 10×75 + 6.25×178 − 5×30 + 5 = 750 + 1112.5 − 150 + 5 = 1,718 kcal/day

A woman with the same measurements would be 166 kcal lower at 1,552 kcal/day.

Variable	Effect on BMR
+1 kg body weight	+10 kcal/day
+1 cm height	+6.25 kcal/day
+1 year of age	−5 kcal/day
Male vs female	+166 kcal/day

Everything runs in your browser — nothing is uploaded.