BMR Calculator

What BMR means

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest just to stay alive — running your heart, lungs, brain, and cell repair. It's the floor of your daily energy needs, typically 60-70% of the calories you burn in a day. BMR doesn't include any movement at all, which is why you should never eat at your BMR to lose weight; you'd be under-fuelling badly.

The Mifflin-St Jeor equation

This calculator uses Mifflin-St Jeor, which research has repeatedly found more accurate for the general population than the older Harris-Benedict equation. It's the same formula used by most registered dietitians.

Worked example

A 30-year-old woman, 165 cm tall, weighing 65 kg:

1. 10 × 65 kg = 650
2. 6.25 × 165 cm = 1,031
3. 5 × 30 years = 150
4. 650 + 1,031 − 150 − 161 = 1,370 calories/day

So her body burns about 1,370 calories a day doing absolutely nothing. Any movement on top of that adds more — which is what the TDEE calculator works out.

What to do with your BMR

• Don't eat at your BMR. It excludes all activity, so eating that little almost always creates too big a deficit. Use TDEE for real calorie targets.
• BMR scales with lean mass, so two people at the same weight can differ meaningfully if one carries more muscle.
• It falls slowly with age (roughly the −5 × age term), which is part of why maintenance calories drop over the years.
• Any formula is an estimate with a margin of error of a few hundred calories. Treat it as a starting point and adjust based on real results.

Frequently asked questions