Calculadora de TMB (Katch-McArdle)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
TMB = 370 + 21,6 × LBM
About this calculator
The Katch-McArdle BMR Calculator estimates basal metabolic rate using lean body mass (LBM). Unlike other formulas that consider total weight, age, and gender, the Katch-McArdle equation is more accurate for individuals with known body composition. The formula is: BMR = 370 + 21.6 × LBM (in kg). This calculator is ideal for athletes, bodybuilders, or anyone who knows their body fat percentage.
How it works: you enter your total weight and body fat percentage. The calculator converts the percentage into fat mass and subtracts it from total weight to get LBM. Then it applies the formula to estimate the calories your body burns at rest. This value is the basis for calculating daily caloric needs, considering physical activity level.
When to use: if you have access to accurate body composition measurements (bioimpedance, skinfolds, DEXA), the Katch-McArdle formula provides a more personalized estimate than traditional formulas (Mifflin-St Jeor, Harris-Benedict). It is useful for planning muscle gain or fat loss diets by adjusting caloric deficit or surplus.
Cautions: accuracy depends on the quality of the body fat measurement. Home methods (simple bioimpedance scales) can have errors up to 5%. The formula assumes LBM is metabolically active, which is valid for most, but may overestimate BMR in individuals with low muscle mass. Always use as a starting point and adjust based on body response.
Frequently asked questions
What is the difference between the Katch-McArdle formula and others like Mifflin-St Jeor?
Katch-McArdle uses lean body mass, ignoring age and gender, making it more accurate for those who know their body composition. Other formulas use total weight, age, and gender, and are better for the general public without body fat data.
Do I need to know my exact body fat percentage?
Not exact, but the more accurate, the better. Use methods like bioimpedance, skinfolds, or DEXA. Visual estimates or simple scales can have significant errors.
How do I use the BMR result for weight loss?
Subtract 300-500 calories from your BMR multiplied by the activity factor to create a caloric deficit. Monitor weight for 2 weeks and adjust as needed.
Does this formula work for older adults?
It works, but accuracy depends on LBM measurement. Older adults may have lower muscle mass, so the formula may overestimate BMR if LBM is underestimated. Individual adjustments are recommended.
Can I use this calculator if I don't know my body fat percentage?
No, because the formula depends on LBM. If you don't have the percentage, prefer calculators like Mifflin-St Jeor or Harris-Benedict, which use total weight.