Basal Metabolic Rate (BMR): Formulas and How to Use Yours

What Is BMR?

Your Basal Metabolic Rate (BMR) is the calories your body burns at complete rest — breathing, circulation, cell production, temperature regulation. For most sedentary people, BMR accounts for 60–75% of total daily calorie burn.

Mifflin-St Jeor Formula (Recommended)

Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5
Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161

Harris-Benedict Formula (Older)

Men: 88.362 + (13.397 × kg) + (4.799 × cm) − (5.677 × age)
Women: 447.593 + (9.247 × kg) + (3.098 × cm) − (4.330 × age)

Mifflin-St Jeor is more accurate for modern populations.

BMR vs. TDEE

BMR is just the baseline. Multiply by an activity factor to get TDEE (your maintenance calories). Eating at BMR without activity would be severe restriction for most people.

What Affects BMR

Muscle mass (more = higher BMR), age (decreases ~1–2%/decade after 30), body size, thyroid function, and dieting history (severe restriction lowers BMR below predicted values).

Frequently Asked Questions

What is the difference between BMR and RMR?

BMR is measured under strict clinical conditions (complete rest, fasted). RMR is measured under less strict conditions and runs 10–20% higher. The terms are often used interchangeably in practice.

Does eating frequently boost metabolism?

No — this is a myth. Total calorie intake over 24 hours determines metabolic rate, not meal frequency. 6 small meals vs. 3 larger meals makes no metabolic difference when calories are equal.