BMR Calculator
Estimate the calories your body burns at complete rest
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Basal Metabolic Rate (BMR) is the number of calories your body needs to keep functioning at rest. It is the foundation of your daily calorie target — multiply BMR by an activity factor to get TDEE. Mifflin-St Jeor is the most accurate for most people; Katch-McArdle is best if you know your body-fat percentage.
How to use this BMR calculator
Choose your gender and one of three formulas — Mifflin-St Jeor (recommended for most people), the classic Harris-Benedict, or Katch-McArdle if you know your body-fat percentage. Then enter your age, height and weight, switching freely between metric (cm·kg) and imperial (in·lb) units. With Katch-McArdle the age field is replaced by a body-fat input, and your result appears instantly with no sign-up.
How to read your result
Your BMR is the energy your body burns at complete rest just to keep you alive — breathing, circulation, temperature and cell repair. It is a floor, not an eating target: routinely eating below your BMR for long periods can slow your metabolism and cost you muscle. Because BMR falls as you lose weight and as you age, recalculate every few months and watch the trend rather than a single number.
The formulas and the science behind them
Mifflin-St Jeor (10×weight + 6.25×height − 5×age, +5 for men or −161 for women) was published in 1990 and is rated by the American Dietetic Association as the most accurate for modern populations. Harris-Benedict dates back to 1919 and remains a widely used classic. Katch-McArdle (370 + 21.6×lean mass) works from lean body mass instead, which makes it the best choice for lean or muscular people who know their body-fat percentage.
Limits and practical tips
Any formula estimates a population average, so your true BMR can differ by roughly ±10% due to genetics, hormones and muscle mass, and accuracy drops for very muscular, elderly or pregnant individuals. BMR alone is not your calorie budget — multiply it by activity with our TDEE calculator, then plan intake with the calorie-deficit, macro and protein calculators. Logging your meals in the CaloNote app shows whether your real-world results match the estimate.
Frequently Asked Questions
- What is the difference between BMR and TDEE?
- BMR is the calories your body burns at complete rest. TDEE is BMR plus the calories burned through daily activity and exercise.
- Which BMR formula is most accurate?
- Mifflin-St Jeor is the most accurate for the general population. Katch-McArdle is better if you know your body-fat percentage.
- Can I increase my BMR?
- Building muscle through strength training raises BMR slightly because muscle is more metabolically active than fat. Crash diets lower it.