Lean Body Mass Calculator
Calculate your lean body mass — the weight of everything in your body except fat. Used to set protein targets and track true fitness progress.
How to use this calculator
Set your height and weight using the sliders, then select your gender. Your lean body mass is calculated instantly using three formulas — Boer, James, and Hume — and averaged for accuracy. You'll also see your estimated fat mass, body fat percentage, and optimal daily protein target based on your lean mass.
Understanding lean body mass
Lean body mass (LBM) is your total weight minus fat — it includes muscle, bone, water, and organs. It's a better measure of fitness progress than total weight because it stays stable or increases when you build muscle, even if the scale doesn't move much. Protein targets based on LBM are more accurate than targets based on total body weight, especially for people carrying extra fat.
Frequently asked questions
LBM formulas compared
The three formulas used in this calculator estimate lean body mass from height and weight. They agree closely for people of average build but diverge for very short, very tall, or obese individuals. Averaging them reduces the error of any single formula.
| Formula | Year | Men | Women |
|---|---|---|---|
| Boer | 1984 | LBM = 0.407W + 0.267H − 19.2 | LBM = 0.252W + 0.473H − 48.3 |
| James | 1976 | LBM = 1.1W − 128(W/H)² | LBM = 1.07W − 148(W/H)² |
| Hume | 1966 | LBM = 0.3281W + 0.3393H − 29.5 | LBM = 0.2296W + 0.3542H − 11.4 |
Typical lean body mass by fitness level
Lean body mass varies significantly with muscle development. These ranges represent approximate LBM at different body composition levels for a 5'10" (178 cm) individual. Actual values depend on bone density and organ size as well.
| Body type | LBM — Men (5'10") | LBM — Women (5'4") |
|---|---|---|
| Sedentary, higher body fat | 120–140 lbs (54–64 kg) | 90–105 lbs (41–48 kg) |
| Average fitness | 140–155 lbs (64–70 kg) | 100–115 lbs (45–52 kg) |
| Fit, regular training | 155–170 lbs (70–77 kg) | 110–125 lbs (50–57 kg) |
| Athletic, dedicated training | 165–185 lbs (75–84 kg) | 120–135 lbs (54–61 kg) |
| Elite athletes / bodybuilders | 185–210+ lbs (84–95+ kg) | 130–150+ lbs (59–68+ kg) |
Why LBM matters more than total weight
The scale shows you one number that contains two very different things: lean mass (muscle, bone, organs, water) and fat mass. Two people at the same weight can have dramatically different health profiles. Tracking LBM over time — rather than just total weight — reveals true body composition progress.
- ·When starting resistance training, the scale may not change but LBM increases and fat decreases — visible body composition changes happen without weight loss
- ·On a fat loss diet, preserving LBM is the primary goal — losing muscle slows metabolism and worsens body composition
- ·Protein targets based on LBM (1.6–2.2g per kg of LBM) are more precise than targets based on total bodyweight, especially for heavier individuals
- ·LBM naturally declines ~3–8% per decade after age 30 (sarcopenia) without resistance training — this is a major driver of age-related metabolic slowdown
- ·LBM improvements from training show up weeks before the scale reflects them, making it an important progress metric
How to increase lean body mass
Building lean mass requires two things simultaneously: a training stimulus and sufficient nutrition. Neither alone is as effective as both together.
- ·Progressive overload — consistently increasing weight, reps, or difficulty over time is the primary driver of muscle growth
- ·Protein intake of 1.6–2.2g per kg of LBM — spread across 3–4 meals of 30–40g each for optimal muscle protein synthesis
- ·Calorie surplus — a modest surplus of 150–300 cal/day supports muscle growth while minimizing fat gain
- ·Compound movements (squat, deadlift, bench, row, press) build the most muscle mass in the shortest time
- ·Sleep 7–9 hours — growth hormone peaks during deep sleep; muscle repair happens primarily at night
- ·Expect 0.5–2 lbs of muscle gain per month in beginners; 0.25–0.5 lbs/month in intermediates