Katch-McArdle BMR Calculator
Enter your weight and body fat percentage to calculate BMR using the Katch-McArdle formula, which is based on lean body mass rather than total weight alone — often considered more accurate for people who are notably lean or muscular, where standard weight-only formulas can be less precise.
How the Katch-McArdle BMR formula works
The Katch-McArdle formula:
Lean body mass (kg) = Weight (kg) × (1 − Body fat % / 100) BMR = 370 + (21.6 × Lean body mass)
Step-by-step calculation
- Convert body fat percentage to a decimal and subtract it from 1.
- Multiply by total body weight in kilograms to find lean body mass.
- Multiply lean body mass by 21.6 and add 370 to get BMR.
Worked example
A person weighing 80 kg at 18% body fat: Lean mass = 80 × (1 − 0.18) = 65.6 kg. BMR = 370 + (21.6 × 65.6) ≈ 370 + 1,417 = 1,787 calories/day.
Frequently asked questions
How is this different from the standard BMR calculator?
The standard BMR Calculator on this site uses the Mifflin-St Jeor formula, which is based on weight, height, age, and sex without needing to know body fat percentage. Katch-McArdle instead uses lean body mass directly, which can be more accurate for people with body composition that differs notably from average — but it requires an accurate body fat percentage measurement to be reliable.
How do I find my body fat percentage?
Common methods include skinfold calipers, bioelectrical impedance scales, DEXA scans, or hydrostatic weighing — accuracy varies by method, and a rough estimate will produce a correspondingly rough BMR estimate here.