How the Body Fat Percentage Method Works
The Katch-McArdle formula estimates your Basal Metabolic Rate (BMR) using your lean body mass instead of just weight, height, and age. This makes it more accurate for people who know their body fat percentage.
The Katch-McArdle Formula
The equation is simple:
BMR = 370 + (21.6 × lean body mass in kg)
Lean body mass is your total weight minus your fat mass. For example, if you weigh 80 kg at 20% body fat, your lean mass is 64 kg, giving a BMR of about 1,752 kcal per day.
When Should You Use Katch-McArdle?
This formula works best when you have a reliable body fat measurement. It is especially useful for:
- Athletes and bodybuilders with above-average muscle mass
- People with very low or very high body fat, where standard formulas may be less accurate
- Anyone who has had a DEXA scan, hydrostatic weighing, or skinfold test
If you do not know your body fat percentage, the Mifflin-St Jeor formula is a great alternative.
Katch-McArdle vs Mifflin-St Jeor
The Mifflin-St Jeor equation uses age, weight, height, and gender. It works well for most people but may overestimate calories for those with high body fat or underestimate for muscular individuals. Katch-McArdle removes this bias by focusing on lean mass alone.
How to Use Our Calculator
Enter your details in the TDEE calculator on our homepage and include your body fat percentage in the optional field. The calculator will automatically apply the Katch-McArdle formula alongside Mifflin-St Jeor and Harris-Benedict, so you can compare results.