Katch Mcardle BMR
Calculator

Unlike Harris-Benedict or Mifflin-St Jeor, which use total body weight, height, age, and sex, the Katch-McArdle formula calculates BMR based solely on lean body mass. This makes it potentially more accurate for people who know their body fat percentage, especially those who are notably lean or muscular.

The formula first requires converting your total weight and body fat percentage into lean body mass, since lean mass, not total weight, is what actually drives your resting energy expenditure. Without an accurate body fat percentage, the result will be only as reliable as that input.

Because it isolates the metabolically active lean mass rather than treating all body weight equally, it avoids overestimating calorie needs for very lean, muscular individuals or underestimating for those with higher body fat, situations where weight-only formulas can be less precise. This makes it popular in strength training and physique-focused communities.

Quite sensitive: since body fat percentage directly determines the lean mass used in the formula, an inaccurate body fat estimate (common with tape-measure or bioelectrical impedance methods) will proportionally skew your calculated BMR. Using a more reliable body fat measurement method improves the accuracy of this result.

If you have a reasonably accurate body fat percentage from a reliable method like DEXA, Katch-McArdle can offer a more personalized estimate, especially if your body composition is atypical for your weight. If you're unsure of your body fat percentage, a weight-based formula like Mifflin-St Jeor may actually be more reliable in practice.