What is the Katch-McArdle BMR calculator?
Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest to keep its vital functions running, such as breathing, circulation, and cell repair. The Katch-McArdle calculator estimates this rate from a single number: your lean body mass, the weight of everything in your body that is not fat.
Because muscle and organs drive most resting energy use, while fat tissue is relatively inactive, the Katch-McArdle equation often produces a more accurate BMR for lean and athletic people than formulas based on total body weight, height, and age.
Formula
The Katch-McArdle equation expresses BMR in kilocalories per day from lean body mass measured in kilograms:
To find your lean body mass, subtract your fat mass from your total weight. If you know your body fat percentage as a fraction, then .
How to use
- Determine your lean body mass in kilograms (from a body composition scan, calipers, or a bioimpedance scale).
- Enter that value in the lean body mass field.
- Read your estimated BMR in kilocalories per day from the result field.
To get your total daily energy needs, multiply the BMR by an activity factor that reflects how active you are.
Worked example
Suppose your lean body mass is 60 kg. Plugging it into the equation:
So a person with 60 kg of lean mass burns about 1666 kcal per day at rest.
FAQ
Why does this formula ignore height and age? The Katch-McArdle equation assumes that lean body mass already captures the factors that matter most for resting metabolism. Since lean mass reflects your muscle and organ tissue directly, height and age add little extra accuracy once you know it.
When should I use Katch-McArdle instead of other BMR formulas? Use it when you have a reliable lean body mass measurement, especially if you are lean or muscular. If you do not know your body composition, an equation like Harris-Benedict or Mifflin-St Jeor, which uses weight, height, and age, is more practical.