What is BMR?
Your basal metabolic rate is the energy your body burns doing nothing at all — keeping the heart beating, lungs breathing and brain running. For most adults it accounts for 60–70% of total daily burn, which is why it anchors every calorie calculation.
How the calculator works
We compute both standard formulas. Mifflin-St Jeor (10 × kg + 6.25 × cm − 5 × age + 5 for men, −161 for women) is the modern standard and the more accurate of the two for today's populations. Harris-Benedict (revised) is the classic 1919 formula, updated 1984, and still appears on food and diet labels.
Common use cases
- The first input to any TDEE or cutting calculation
- Checking that a diet plan is not below a sane floor
- Understanding why smaller, older bodies need less food
Formula & context
BMR never includes exercise — that is what TDEE adds. Eating below your BMR long-term is a common red flag in crash diets; most sustainable cuts sit between BMR and TDEE.
Frequently Asked Questions
Which formula is more accurate?
Mifflin-St Jeor — it was validated against indirect calorimetry in the 1990s and outperforms Harris-Benedict by roughly 5%.
Why does BMR fall with age?
Lean mass declines with age; because muscle is metabolically active, the burn rate falls with it. Resistance training slows that curve.
Should I eat below my BMR?
Short-term it is survivable, but sustainable deficits usually land between BMR and TDEE so training and recovery stay intact.
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