BMR (Katch-McArdle)
Resting calories from lean body mass.
Formula
Variables
Example
LBM 60 kg ⇒ 370 + 1296 = 1666 kcal
How it works
The Katch-McArdle equation estimates your basal metabolic rate, which is the number of calories your body burns at complete rest to keep vital functions running. It is based on lean body mass because muscle, organs, and other non-fat tissues are much more metabolically active than body fat, so two people with the same weight can have very different calorie needs if their body composition differs. The constant 370 and multiplier 21.6 come from fitting the formula to measured resting energy expenditure data.
When to use it
Use this formula when you know or can reasonably estimate lean body mass, such as from a DEXA scan, body-fat calipers, bioimpedance, or a well-supported body-fat estimate. It is especially useful for athletes, people changing body composition, or anyone whose calorie needs are better predicted by muscle mass than by total body weight.
Worked example, step by step
Given: LBM = 72 kg Formula: BMR = 370 + 21.6 × LBM Substitute: BMR = 370 + 21.6 × 72 Multiply: 21.6 × 72 = 1555.2 Add: 370 + 1555.2 = 1925.2 Final answer: BMR ≈ 1925 kcal/day
Common mistakes to avoid
- Using total body weight instead of lean body mass
- Forgetting that the result is an estimate of resting calories, not total daily calories
- Mixing kilograms and pounds without converting to kilograms first
Did You Know?
Because it uses lean mass rather than total weight, it is far more accurate for very muscular or very lean people.
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