Lean Body Mass Calculator

Lean body mass (LBM) is your total body weight minus your fat mass. It includes muscle, bone, organs, connective tissue, and the water in those tissues. It is often used as a base for protein targets and drug dosing.

If you have a body-fat percentage from a reasonable measurement (Navy circumference, skinfold calipers, DEXA, bioimpedance), the Body fat % method is the most direct. The formula methods (Boer, James, Hume) only use height and weight, so they cannot account for individual body composition.

Each formula was derived from a different population sample. Boer (1984), James (1976), and Hume (1966) all return slightly different values, especially at the extremes of body weight. Use them as a range, not a single number.

No. DEXA (dual-energy X-ray absorptiometry) is a clinical body composition measurement. The formulas on this page are population-level estimates from height, weight, and (optionally) a body-fat percentage. They are educational estimates only.

Common uses include scaling protein intake to lean mass instead of total weight, tracking changes during fat loss or muscle gain, and as a sanity check against scale weight when body composition is shifting.

No. The calculator is an educational tool. Body composition matters for many health questions, but interpreting the number for clinical purposes is the job of a clinician or registered dietitian.

For men: 75-85% LBM (15-25% body fat) is considered healthy. Athletes often have 85-94% LBM (6-15% body fat). For women: 69-79% LBM (21-31% body fat) is healthy. Female athletes are typically 80-86% LBM (14-20% body fat). Women naturally have higher essential fat requirements due to reproductive hormones, so don't aim for male athletic LBM ranges if you're a woman.

Strength training is the most effective method — progressive overload (gradually lifting heavier weights or doing more reps) signals muscle growth. Combined with adequate protein intake (1g per lb of LBM), 7-9 hours of sleep, and slight calorie surplus, expect to gain 0.5-2 lbs of LBM per month for natural beginners. Advanced trainees gain LBM much more slowly (1-3 lbs per year).

Yes. LBM includes muscle, bone, organs, blood, AND body water. About 60-70% of LBM is water. This is why hydration significantly affects body composition measurements — being dehydrated can make your LBM appear 2-5 lbs lower than it actually is.

Each formula was developed using different population samples and statistical methods. Boer was developed for medical dosing, James for athletic populations, Hume for general clinical use. They typically produce results within 5-10 lbs of each other. For most purposes, picking any one formula and using it consistently is more important than which specific formula you choose — the trend over time matters more than the absolute number.