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
Why lean body mass drives your metabolism
Lean tissue is metabolically expensive to maintain — muscle, organs, and the rest of your fat-free mass burn calories around the clock, while stored fat is comparatively cheap to keep. That is why your resting metabolic rate tracks lean body mass far more closely than it tracks total weight, and why two people of the same scale weight can have noticeably different calorie needs. Building or protecting LBM is one of the few levers that raises the floor of how many calories you burn at rest.
- ·Resting metabolic rate scales with lean mass — more LBM means a higher baseline calorie burn, even on rest days
- ·When LBM is lost (through crash dieting or age-related sarcopenia), resting metabolism falls and weight regain becomes easier
- ·Scaling protein to LBM rather than total weight (roughly 1.6–2.2g per kg of LBM) targets the tissue that actually needs it, which matters most for people carrying extra fat
- ·A small surplus plus resistance training adds LBM; a deficit plus resistance training and high protein preserves it while fat comes off
- ·Tracking LBM, not just bodyweight, tells you whether a diet is costing you the very tissue that keeps your metabolism up