Lean Body Mass Calculator
Lean body mass (LBM) is everything in your body except fat: muscle, bone, organs and water. This calculator estimates your LBM with three validated formulas, or exactly from your body fat percentage if you know it.
Lean body mass represents everything in your body except fat. Healthy lean mass ranges are roughly 75% to 86% of body weight for men and 69% to 79% for women. Boer is the clinical default for drug dosage and metabolic calculations.
Estimated Lean Body Mass
78.5% of Body WeightYour lean body mass represents everything except fat tissue (muscles, organs, bones, and water). An estimated 21.5% consists of body fat.
Lean Mass %
78.5%
Of total body mass
Implied Fat %
21.5%
Fat mass share
Formula Comparison
| Formula | Lean Mass | LBM % | Notes |
|---|---|---|---|
| Boer (Recommended) | 58.9 kg | 78.5% | Widely validated clinical standard |
| James | 59.8 kg | 79.7% | Standard pharmacokinetic formula |
| Hume | 55.5 kg | 74% | Total body water regression equation |
The Boer formula is the clinical default for drug dosage and metabolic calculations.
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Clinical Equations
WHO, CDC, ACSM & Mifflin-St Jeor
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How to use Lean Body Mass Calculator
- 1Select your sex and enter your current body weight.
- 2Enter your height in metric or imperial units.
- 3Optionally enter your body fat percentage if measured via DEXA or calipers.
- 4Compare your lean mass across Boer, James, and Hume clinical formulas.
Why lean body mass matters
Knowing your lean mass helps you set precise protein targets (1.6 to 2.2 g/kg of LBM) and use advanced metabolic formulas like Katch-McArdle for basal metabolic rate.
During fat loss or cutting diets, tracking LBM ensures you are shedding adipose tissue while preserving vital skeletal muscle mass.
Clinical formula differences
The Boer (1984) formula is widely accepted in pharmacokinetics for dosing medications and evaluating fluid volumes.
James (1976) and Hume (1966) equations offer alternative regression analyses based on height-to-weight relationships and total body water.
Frequently Asked Questions
What is a normal lean body mass percentage?
Roughly 75 to 86% of body weight for men and 69 to 79% for women, the inverse of healthy body fat ranges.
Is lean body mass the same as muscle mass?
No. LBM includes bone, organs and water, so it's always higher than muscle mass alone.
Which LBM formula should I use?
Boer is the default and performs well for most adults; use the body-fat method if you have a reliable body fat measurement.
Related Calculators
Body Fat Calculator
Estimate your body fat percentage using the US Navy tape method or Deurenberg BMI equation.
BMR Calculator
Calculate your Basal Metabolic Rate using Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle.
Protein Calculator
Calculate your daily protein requirements based on body weight, fitness goals, and training intensity.
Calorie Surplus Calculator
Calculate your bulking calories and macro breakdown for clean muscle gain without excess fat.
TDEE Calculator
Estimate your Total Daily Energy Expenditure and discover your true maintenance calories.
Scientific Sources & Evidence
- World Health Organization (WHO) — Body Mass Index Classification
- CDC Growth Charts — BMI-for-age LMS Percentiles
- Mifflin et al. (1990) — Basal Metabolic Rate Predictive Equations
- NICE Guideline NG246 — Identification and Management of Overweight and Obesity
- American College of Sports Medicine (ACSM) — Exercise Testing & Prescription
- European Food Safety Authority (EFSA) — Dietary Reference Values for Water