Katch-McArdle Calculator — Free
Calculate your BMR and TDEE from lean body mass with the Katch-McArdle formula — the most accurate calorie estimate for lean, muscular and athletic bodies. Just enter your weight and body fat %.
Katch-McArdle Calculator
Not used in the formula — it only sets the minimum healthy body-fat floor.
Range: 30–300 kg · up to 2 decimals
Optional — used only to apply teen-safety guidance. It does not change your BMR.
Range: 3–45% · up to 2 decimals
Not sure? See typical body fat ranges
Men: athletic 6–13% · fit 14–17% · average 18–24% · higher 25%+
Women: athletic 14–20% · fit 21–24% · average 25–31% · higher 32%+
A rough estimate still gives a usable number — for a precise reading, use the Body Fat Calculator below.
Add your height (optional — enables an underweight safety check)
Enter your height in centimeters (e.g., 170 cm)
Not used in the Katch-McArdle BMR — only to check your weight isn't already in the underweight range before showing fat-loss targets.
*This calculator is for informational purposes only. Please consult a healthcare professional before making any health decisions. See our medical disclaimer for more information.
Quick Answer
What Is the Katch-McArdle Formula?
The Katch-McArdle formula calculates your Basal Metabolic Rate from lean body mass instead of age, height and gender: BMR = 370 + 21.6 × lean body mass (kg), where lean mass = weight × (1 − body fat% ÷ 100). Your Total Daily Energy Expenditure is then BMR × your activity multiplier. Because muscle is what actually drives your resting metabolism, this lean-mass approach is usually the most accurate calorie estimate for lean, muscular, and athletic people who know their body fat percentage. Enter your weight and body fat % above to get your exact BMR, TDEE and calorie targets.
The Katch-McArdle Formula: BMR from Lean Body Mass
Most BMR equations (Mifflin-St Jeor, Harris-Benedict) estimate metabolism from age, height, weight and sex. The Katch-McArdle equation takes a different, more direct route: it derives BMR from your lean body mass — everything that isn't fat. Since muscle and organs, not fat, are what burn most of your resting calories, a person with more lean mass has a higher metabolic rate even at the same scale weight. That is the insight Katch-McArdle captures and weight-only formulas miss.
Step 1 — Lean Body Mass:
Lean mass (kg) = Weight (kg) × (1 − Body Fat% ÷ 100)
Step 2 — Basal Metabolic Rate:
BMR = 370 + (21.6 × Lean mass in kg)
Step 3 — Total Daily Energy Expenditure:
TDEE = BMR × Activity multiplier (1.2 – 1.9)
Example: an 80 kg person at 18% body fat has 65.6 kg lean mass → BMR = 370 + 21.6 × 65.6 ≈ 1,787 kcal. At moderate activity (×1.55), TDEE ≈ 2,770 kcal/day.
Source: McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance (8th ed., 2014). The constant 370 and the 21.6 kcal/kg coefficient trace to the peer-reviewed Cunningham (1991) fat-free-mass equation (Am J Clin Nutr 54(6):963–969), the lean-mass terms used across the fitness and sports-science literature. If you already know your fat-free mass, the Cunningham Equation Calculator runs the same 370 + 21.6 × FFM maths directly.
Katch-McArdle vs Mifflin-St Jeor: Which Should You Use?
The practical difference is body composition. Two people who both weigh 80 kg get the same BMR from Mifflin-St Jeor — but if one is 12% body fat and the other 30%, their true metabolic rates differ by hundreds of calories. Katch-McArdle separates them because it works from lean mass. The trade-off is that it needs an accurate body fat number; a bad body fat estimate makes it less reliable than the simpler Mifflin formula.
Rule of thumb: if you train seriously and know your body fat %, Katch-McArdle is the more precise tool. If you have an average build or don't know your body fat, use Mifflin-St Jeor. For a fully worked, number-by-number comparison of one body through both, see Katch-McArdle vs Mifflin-St Jeor — or, against the classic 1919 formula, Katch-McArdle vs Harris-Benedict. You can also run all three formulas side by side on our TDEE Calculator, then turn your maintenance number into a fat-loss plan with the Calorie Deficit Calculator.
Who Should Use the Katch-McArdle Calculator?
Katch-McArdle is the formula of choice for anyone whose body composition is meaningfully different from average: strength athletes and bodybuilders carrying extra muscle, lean endurance athletes, and people deep into a body-recomposition phase who track their body fat closely. For these users the lean-mass model avoids the systematic error that height/weight formulas make on muscular bodies. Women can start from the pre-set Katch-McArdle calculator for women. If you don't yet know your body fat percentage, estimate it first with our Body Fat Percentage Calculator, then come back for a precise BMR and TDEE — or read how the method works under its plainer name, calculating BMR from body fat percentage.
Katch-McArdle Calculator — Limitations
- ⚠The formula is only as accurate as your body fat measurement — a guessed body fat % can shift BMR by 100–200 kcal/day. Use calipers, a DEXA scan, or a consistent method for the best result.
- ⚠BMR and TDEE are population estimates; individual metabolism varies by ±10% due to genetics, thyroid function, sleep and prior dieting history.
- ⚠Activity multipliers are broad brackets — non-exercise movement (NEAT) varies widely between people with the same labelled activity level.
- ⚠Like all static formulas, it does not model metabolic adaptation: as you lose weight your TDEE drops, so recalculate every 4–5 kg (10 lb) of change.
- ⚠Calorie targets here are general guidance, not a medical prescription. Anyone with a metabolic, thyroid or eating-disorder history should consult a clinician or registered dietitian before setting a deficit.
Safe Execution Protocol: Katch-McArdle Next Steps
Before acting on your results, follow these expert-validated guidelines to protect metabolic health and long-term progress:
- Measure body fat with a consistent method and re-measure under the same conditions — switching methods mid-cut introduces noise that looks like a metabolism change.
- Never eat below your BMR for extended periods without medical supervision — it accelerates muscle loss and metabolic adaptation.
- Set protein from lean body mass (1.8–2.2 g/kg of lean mass) to preserve muscle during a deficit — a core advantage of knowing your lean mass.
- Recalculate your TDEE every 4–5 kg (10 lb) of weight change, since lean mass and maintenance calories both shift as you progress.
- Treat the activity multiplier conservatively — when fat loss stalls, drop one activity bracket before cutting calories further.
Use the clinical routing dashboard below to execute these steps safely with verified professional resources.
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Related Katch-McArdle Calculators
Have a more specific question? These focused pages all run the same lean-mass engine (BMR = 370 + 21.6 × lean mass) as the calculator above:
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Each calculator feeds into the next — your data carries forward automatically through every step.
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BMR
The calories your body burns at complete rest — via Mifflin-St Jeor, Harris-Benedict and Katch-McArdle.