What is the most accurate BMR formula?

For lean, trained individuals: Katch-McArdle. For the general population: Mifflin-St Jeor. For obesity: Harris-Benedict or clinical indirect calorimetry. No calculator beats a metabolic cart in practice.

How do I measure lean body mass accurately?

DEXA and BodPod are gold-standard (±1–2%). 7-site skinfold (Jackson-Pollock) is a solid practitioner tool. Consumer BIA scales vary 3–8% — useful for tracking changes, unreliable for absolute values.

Does Katch-McArdle give a higher or lower BMR?

For lean athletic individuals: usually higher than Mifflin-St Jeor by 50–150 cal/day. For general population near average body-fat: the two formulas converge within ~3%.

Katch-McArdle BMR Calculator

Mifflin-St Jeor is the default equation for the general population — but it systematically <strong>under-estimates BMR</strong> in lean, muscular athletes by 50–150 calories per day. The Katch-McArdle equation uses your lean body mass (LBM) instead of total weight, making it the most accurate choice when you know your body-fat percentage and are below ~20% body fat. This calculator applies <em>370 + (21.6 × LBM in kg)</em> and gives you a TDEE projection matched to your training load — essential for any lifter or athlete running a precise cut, maintenance, or bulk.

Written by Marcus Reed, CISSN· Certified Sports Nutritionist (ISSN)

Medically reviewed by Dr. Amara Johnson, MD

Last reviewed April 20, 2026

5 min read

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Key Facts: BMR Calculator (Katch-McArdle) for Lean Athletes

✓Formula: BMR = 370 + (21.6 × lean body mass in kg)
✓Accuracy advantage kicks in below ~20% body fat
✓Requires a reliable body-fat estimate (DEXA, BodPod, 7-site skinfold)
✓Bio-impedance scales err by 3–8% — use cautiously

Special Considerations for Lean / trained individuals

⚡Invalid with inaccurate body-fat measurement — garbage in, garbage out
⚡Not appropriate for obese populations (LBM proportions differ)
⚡Recalculate every 4–8 weeks during a cut — LBM changes
⚡Combine with activity multipliers just like Mifflin-St Jeor

BMR Calculator (Katch-McArdle) for Lean Athletes: Frequently Asked Questions

Use Katch-McArdle when you have a reliable body-fat measurement and sit below ~20% body fat. Above that, Mifflin-St Jeor matches reality just as well and requires less data. See our standard BMR calculator for the baseline.

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Medical Disclaimer: This calculator provides estimates based on population-level research formulas. Individual results may vary. Consult a healthcare professional before starting any diet or exercise program. This tool is not a substitute for professional medical advice.