Lean Body Mass Calculator
Estimate your lean body mass (LBM) from height and weight. Compare three medical formulas to support dosing, body composition analysis, and fitness planning.
Inputs
Select unit system, then enter sex, height, and weight.
Lean Body Mass Estimates
Boer formula
63.5 kg (139.9 lb)
Broadly used in anesthesia and renal dosing.
James formula
-1942.2 kg (-4281.8 lb)
Useful for non-obese individuals; may underestimate at higher BMI.
Hume formula
59.4 kg (131 lb)
Developed from hospital patient data; common in pharmacokinetics.
Average lean body mass
-606.4 kg (-1337 lb) — Useful for quick reference when a single number is needed.
How to Use This Calculator
Gather measurements
Use a calibrated scale and a stadiometer or wall ruler. Wear light clothing for consistency.
Review multiple formulas
Boer performs well across BMI ranges, James is best for normal BMI, and Hume is popular in clinical dosing. Compare them before deciding.
Apply in context
Use lean body mass to set protein targets, estimate basal metabolic rate, or adjust medication dosages according to clinical guidance.
Formula
- Boer: Male LBM = 0.407 × weight + 0.267 × height − 19.2; Female LBM = 0.252 × weight + 0.473 × height − 48.3 (weight in kg, height in cm)
- James: LBM = weight × (1 − (weight ÷ (denominator × height²))), where denominator is 1.1 (male) or 1.07 (female) and height is in meters.
- Hume: Male LBM = 0.32810 × weight + 0.33929 × height − 29.5336; Female LBM = 0.29569 × weight + 0.41813 × height − 43.2933.
All inputs are converted to metric units before applying formulas.
Understanding Lean Body Mass
Lean body mass represents your body mass minus fat. It includes muscle, bone, organs, and water. Tracking lean mass helps in evaluating training adaptations, planning nutrition, and calculating medication doses that rely on water distribution.
Use lean mass in combination with body fat percentage, strength progression, and metabolic markers to gain a full picture of physical health.
Frequently Asked Questions
Which formula should I trust?
Boer is widely recommended for a broad BMI range. James suits normal BMI individuals, and Hume is common in pharmacokinetics. Compare them and consider clinical guidance.
Can bodybuilders rely on these formulas?
Highly muscular individuals may see underestimation. Combine formula results with DEXA scans or hydrostatic weighing for precision.
Do I need body fat percentage for lean mass?
These formulas infer lean mass from height and weight. Measuring body fat directly can provide a more individualized result.
How often should I recalculate?
Recalculate after significant weight change (±2–3 kg) or quarterly during fitness programs to monitor progress.