Katch–McArdle Calculator.
Estimate resting energy from weight and body-fat percentage. The example uses 20% body fat; replace it with your own measurement.
Your energy at rest
Resting energy is only part of your daily needs. It is not a daily food target.
Calculated from: 65.0 kg · 20% Body fat
Fat-free mass: 52.0 kg · 370 + 21.6 × 52.0
Compare all resting equations →From fat-free mass to resting calories
Fat-free mass = weight in kilograms × (1 − body-fat percentage ÷ 100). Katch–McArdle resting energy = 370 + 21.6 × fat-free mass. Fat-free mass includes all non-fat tissue; it is not simply muscle mass. Age, height and sex are not direct inputs to this equation.
80 kg at 20% body fat: 64 kg fat-free mass → 370 + 21.6 × 64 ≈ 1,752 kcal/day
At the same weight, 15% body fat produces about 1,839 kcal and 25% produces 1,666 kcal. Input error carries into the result. Without a useful body-fat measurement, choose the Mifflin calculator instead of copying the 20% example. Our methods page documents the implemented equation.
Methods & references
An informational tool; no medical review is claimed. Activity factors and caution thresholds are product planning conventions. Citations do not imply endorsement.
Use the estimate as a starting point.
Track weight and intake under consistent conditions for a few weeks. Adjust the estimate to match your longer-term trend.
Keep your plan connected.
Use the same details across your nutrition tools.
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Track body weight and calorie intake.
Explore toolFind your baseline
Enter your details and choose the activity level that looks like an ordinary week.
Choose a direction
Maintain, lose, or gain. Use a manageable change rather than chasing the lowest number.
Check the bigger picture
Track consistent observations over a few weeks. Adjust as your needs change.
How the calculator works
Equations, assumptions and limitations.
Does Katch–McArdle need age, height or sex?
The equation uses weight and body-fat percentage to estimate fat-free mass. It does not directly use age, height or sex. Its output is resting energy, not total daily expenditure.
Can I use it without knowing my body fat?
Body-fat percentage is required for this equation. The 20% example is not a recommended value. Use Mifflin–St Jeor when you do not have a useful measurement.
How much does body-fat error matter?
At 80 kg, a five-percentage-point difference in body fat changes the resting estimate by about 86 kcal/day. Adding an uncertain input does not guarantee a better estimate.