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Lean Body Mass Calculator

Estimate your lean body mass, the weight of everything except fat, using the Boer and Hume formulas or your body fat percentage.

Results

ItemValue
Formula results are estimates for adults. They do not know your actual muscle, so very muscular or very lean people may get less accurate numbers. A DEXA scan measures body composition directly. This is not medical advice.

Quick Answer

Lean body mass is your weight minus your body fat. The Boer formula for men is 0.407 × weight (kg) + 0.267 × height (cm) − 19.2. A man who weighs 180 lb and is 5 ft 10 in tall has an estimated lean body mass of 135.6 lb (61.5 kg). If you know your body fat percentage, LBM = weight × (1 − body fat %).

Last updated: 2 November 2026 ·How we calculate this: the Boer and Hume formulas

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Table of Contents

How This Lean Body Mass Calculator Works

Enter your sex, weight and height. The calculator estimates your lean body mass with two published formulas, Boer and Hume, which use height and weight. If you know your body fat percentage from a scan or scale, enter it too for a more direct result.

Quick explanation: lean body mass includes muscle, bone, organs, skin and water. Everything except fat.

  • Boer: often used in medicine, including for obese patients.
  • Hume: an older formula that gives similar results.
  • Body fat %: the most direct way if you have a good measurement.

How to Use the Lean Body Mass Calculator

  1. Choose your sex and units.
  2. Enter your weight.
  3. Enter your height.
  4. If you know your body fat percentage, enter it. Otherwise leave it blank.
  5. Press Calculate and compare the Boer and Hume estimates.

Core Formulas

  • Boer, men: 0.407W + 0.267H − 19.2
  • Boer, women: 0.252W + 0.473H − 48.3
  • Hume, men: 0.32810W + 0.33929H − 29.5336
  • Hume, women: 0.29569W + 0.41813H − 43.2933
  • From body fat: LBM = weight × (1 − body fat % ÷ 100)

W is weight in kilograms and H is height in centimeters. Results are in kilograms.

Key Terms

  • Lean body mass (LBM): body weight minus fat: muscle, bone, organs, skin and water.
  • Fat mass: the weight of all fat in the body.
  • Body fat percentage: fat mass as a percent of total body weight.
  • DEXA scan: a low-dose X-ray scan that measures fat, lean tissue and bone.
  • Fat-free mass: body weight minus all fat, very close to lean body mass.

Worked Example

A woman weighs 65 kg and is 165 cm tall.

  • Boer = 0.252 × 65 + 0.473 × 165 − 48.3
  • Boer = 16.38 + 78.05 − 48.3 = 46.1 kg
  • Estimated body fat = 65 − 46.1 = 18.9 kg, or about 29%

Real-Life Examples

  • Setting protein: many athletes base protein on lean mass. At 62 kg of lean mass, 2 g per kg is about 123 g a day.
  • Tracking a diet: if your weight falls but lean mass holds steady, you are mainly losing fat.
  • Using a body fat scale: 200 lb at 25% body fat is 150 lb of lean mass.
  • Comparing estimates: for a 5 ft 4 in, 140 lb woman, Boer gives 98.3 lb and Hume gives 95.8 lb.

Lean Body Mass vs Fat-Free Mass

  • Fat-free mass: body weight minus all fat.
  • Lean body mass: almost the same, but it includes the small amount of fat inside cell membranes, a few percent of weight.
  • In practice: the two terms are often used to mean the same thing.
  • Body fat %: the other side of the same number. Our Body Fat Calculator estimates it from body measurements.

Estimated Lean Body Mass by Height and Weight (Boer)

Estimates only. Your real lean mass depends on how much muscle you have.

HeightWeightMenWomen
5 ft 2 in120 lb99 lb88 lb
5 ft 4 in140 lb110 lb98 lb
5 ft 6 in150 lb117 lb106 lb
5 ft 8 in160 lb124 lb114 lb
5 ft 10 in180 lb136 lb124 lb
6 ft 0 in200 lb147 lb135 lb
6 ft 2 in220 lb158 lb145 lb

What Affects Lean Body Mass

  • Strength training: builds muscle, the main part of lean mass you can change.
  • Protein: enough protein helps keep muscle, especially while losing weight.
  • Age: lean mass tends to fall with age without training.
  • Hydration: water is part of lean mass, so it can change day to day.

Common Mistakes to Avoid

  • Treating the result as exact. Formulas estimate from height and weight, not your real muscle.
  • Mixing units. Make sure the unit setting matches your numbers.
  • Using a poor body fat reading. Home scales can be off by several percent.
  • Comparing different methods. Track changes with the same method each time.
  • Using it for children. These formulas are made for adults.

Frequently Asked Questions

Your total weight minus your body fat. It includes muscle, bones, organs, skin and water.

Boer is often preferred in medicine and tends to work well across body sizes. If you have a good body fat measurement, that is usually more accurate.

Multiply your weight by (1 − body fat % ÷ 100). At 180 lb and 20% body fat, LBM is 144 lb.

It depends on height, sex and training. For many adults, lean mass is about 60% to 90% of body weight.

They were built from different groups of people, so they give slightly different estimates.

Yes. Strength training and enough protein can add muscle, which raises lean mass.

Yes. Water is a large part of lean mass, so the number can move a little from day to day.

No. Muscle is only part of lean mass. Bone, organs and water are included too.

Some medicines spread mainly into lean tissue, so doctors may dose by lean mass rather than total weight.

They are fair estimates for average adults, but can be off for athletes or people with very high or low body fat.

Some diets set protein or calories from lean mass, such as the Katch-McArdle BMR formula.

No. These formulas are for adults. Children’s body composition changes as they grow.

References & Sources

SourceUsed ForLink
Wikipedia, Lean body mass The Boer and Hume formulas. https://en.wikipedia.org/wiki/Lean_body_mass
Yu S, et al. (2013), Lean body mass: prediction equations in healthy adults, BMC Pharmacology & Toxicology How lean body mass formulas are built and tested. https://pmc.ncbi.nlm.nih.gov/articles/PMC3833312/