BMR Calculator

Your Basal Metabolic Rate represents the foundation of all calorie planning. Think of it as the "floor" — the minimum calories your body needs just to stay alive, with no movement whatsoever. BMR accounts for the energy used by your heart, lungs, brain, kidneys, and every cell in your body running their basic functions over 24 hours.

For most people, BMR represents 60–75% of total daily calorie expenditure. This means even if you sit completely still all day, you burn a significant number of calories. The misconception that "a slow metabolism" causes weight gain is partially true but often overstated — true metabolic differences between people of similar size and composition are generally small (200–400 calories). Activity and food choices drive far larger differences.

The two formulas shown here — Mifflin-St Jeor and Harris-Benedict — are both validated predictive equations based on population studies. For most adults, they agree within 5–10%. If you have body fat measurements available, use the Katch-McArdle formula (accessible via our Lean Body Mass and FFMI calculators) for a potentially more accurate estimate.