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The Katch-McArdle formula estimates Basal Metabolic Rate (BMR) as BMR = 370 + 21.6 x lean body mass (kg). Unlike the Harris-Benedict or Mifflin-St Jeor formulas, it is driven directly by lean mass rather than total weight, which can make it more accurate for people with an atypical muscle-to-fat ratio — provided the body-fat percentage input is itself accurate. This is a standard published estimation formula, not a medical measurement — consult a doctor or registered dietitian for individualized guidance.
How it works
Enter your weight and body fat percentage. The tool calculates lean body mass, then applies the Katch-McArdle formula to estimate BMR.
- Enter weight (kg).
- Enter body fat (%).
- Click Calculate to see your results.
Examples
An 80kg person at 20% body fat
Lean mass = 64kg. BMR = 370 + 21.6 x 64 = 1,752 kcal/day.
Who should use it
- Estimating BMR for athletes or muscular individuals where standard formulas may be less accurate.
- Building a more personalized calorie target on top of BMR.
Industry applications
- Sports nutrition and coaching
- Fitness and personal training
Advantages
- Directly accounts for lean mass rather than total weight.
- Can be more accurate than age/sex-based formulas for muscular or very lean individuals.
Limitations
- Highly dependent on the accuracy of the body fat percentage input.
- Requires an extra measurement (body fat %) that other BMR formulas don't need.
Common mistakes to avoid
- Using an inaccurate body fat percentage estimate, which directly skews the BMR result.
- Confusing BMR (calories at complete rest) with TDEE (total daily calories including activity).
Best practices
- Use a consistent, reasonably accurate body fat measurement method for the most meaningful BMR estimate.
Tips
- Add an activity multiplier on top of this BMR result to estimate total daily calorie needs (TDEE).