Katch-McArdle Calculator

The core logic behind the Katch-McArdle formula revolves around your lean body mass, because muscle tissue demands significantly more energy to maintain than adipose (fat) tissue. If you already know your lean body mass directly in kilograms, the base BMR formula is expressed as:

BMR = 370 + (21.6 × LBM)

Where LBM is your Lean Body Mass in kilograms. If you do not have your LBM pre-calculated, but you know your total weight and body fat percentage, you first derive it using your total weight and body fat percentage: LBM = ((100 - Body Fat Percentage) / 100) × Total Weight. Furthermore, if you only have your total weight in kilograms and your height in centimeters, sex-specific formulas can estimate your LBM first, such as: Men LBM = (0.407 × Weight) + (0.267 × Height) - 19.2 and Women LBM = (0.252 × Weight) + (0.473 × Height) - 48.3.

Let us walk through a practical example for an individual using the Katch-McArdle equation. Imagine a female athlete weighing 70 kg with a measured body fat percentage of 20 percent.

Step 1: Calculate Lean Body Mass (LBM)
LBM = ((100 - 20) / 100) × 70 kg
LBM = 0.80 × 70 = 56 kg of lean mass.

Step 2: Apply the Katch-McArdle BMR Formula
BMR = 370 + (21.6 × 56)
BMR = 370 + 1,209.6 = 1,579.6 calories per day.

This means her body expends approximately 1,580 calories daily just to sustain vital organ functions at rest, serving as a robust foundation for calculating total daily energy expenditure (TDEE).

To get the most accurate results from this calculator, ensure your body fat percentage is measured using reliable methods such as a DEXA scan, hydrostatic weighing, or professional skinfold calipers rather than unreliable bioimpedance bathroom scales. Remember that your BMR only represents baseline calorie burn; you must multiply this figure by your daily activity factor (PAL) to determine your true total energy expenditure for weight management goals.