Katch-McArdle TDEE Calculator
Estimate daily calorie needs from lean body mass using the Katch-McArdle formula and your activity level.
How it works
LBM = weight × (1 − body-fat%) · BMR = 370 + 21.6 × LBM(kg) · TDEE = BMR × activity
The Katch-McArdle equation estimates resting metabolism from lean body mass instead of total weight, on the reasoning that muscle and organs — not fat — drive most calorie burn. That makes it more accurate than height-and-weight formulas for lean or very muscular people, provided you have a reasonable body-fat estimate. Multiplying the resulting BMR by an activity factor gives your total daily energy expenditure (TDEE), the calories to maintain weight.
Worked example
A 170 lb person at 20% body fat has 136 lb (61.7 kg) of lean mass. BMR = 370 + 21.6 × 61.7 ≈ 1,703 kcal; at a moderately active factor of 1.55, TDEE ≈ 2,639 kcal per day.
Frequently asked questions
When is Katch-McArdle better than the Mifflin formula?
When you know your body-fat percentage and are leaner or more muscular than average. Because it works from lean mass, it avoids overestimating needs for very lean people and underestimating for very muscular ones.
How do I find my body-fat percentage?
Methods range from skinfold calipers and bioimpedance scales to DEXA scans. Any estimate feeds the formula; the more accurate your body-fat figure, the more reliable the TDEE.
Why subtract 500 calories for weight loss?
A 500 kcal daily deficit is about 3,500 kcal a week, the rough energy in a pound of fat — a common target for losing roughly 0.5 kg to 1 lb per week.
Related calculators
This is a general educational estimate, not medical or dietary advice. Weight, body composition and energy needs respond differently for everyone — for a plan tailored to you, talk to a doctor or registered dietitian.