Katch-McArdle Calculator

The Katch-McArdle formula calculates Basal Metabolic Rate (BMR) using lean body mass rather than total body weight. The equation is: BMR = 370 + (21.6 × Lean Body Mass in kg). Because it accounts for muscle mass directly, it tends to be more accurate than formulas that rely solely on age, sex, height, and weight.

Lean body mass (LBM) is calculated by subtracting your fat mass from your total body weight. The formula is: LBM = Weight × (1 − Body Fat% / 100). For example, a person weighing 75 kg with 20% body fat has an LBM of 60 kg.

BMR (Basal Metabolic Rate) is the number of calories your body needs at complete rest just to sustain basic functions like breathing and circulation. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor — it represents the total calories you burn in a day including exercise and daily movement. To maintain your current weight, your calorie intake should match your TDEE.

No — the Katch-McArdle formula is the same for both males and females. Because it uses lean body mass directly rather than applying separate sex coefficients, it naturally accounts for differences in body composition between men and women. This is one of its key advantages over formulas like Harris-Benedict.

Yes. Multiply your Katch-McArdle BMR by an activity multiplier to get your TDEE. Common multipliers range from 1.2 (sedentary) to 1.9 (very intense daily exercise). This calculator does that automatically when you select your activity level.

The main limitation is that it requires an accurate body fat percentage measurement, which can be difficult to obtain without professional tools. Inaccurate body fat estimates will lead to inaccurate BMR results. Additionally, like all BMR formulas, it provides an estimate — individual metabolism can vary due to genetics, hormones, and health conditions.

Common alternatives include the Mifflin-St Jeor equation and the Harris-Benedict equation, both of which use age, sex, height, and weight instead of lean body mass. The Mifflin-St Jeor equation is generally considered the most accurate for the general population, while Katch-McArdle is preferred for athletes or individuals with known body fat percentages.

BMR varies widely based on body composition, age, and size. For most adults, BMR typically ranges from 1,200 to 2,500 calories per day. A higher lean body mass generally produces a higher BMR, which is why strength training can support a higher resting metabolic rate over time.