Lean Body Mass Calculator

Estimate lean body mass (LBM) using empirical formulas or calculate directly from body fat percentage.

Body Settings

Gender

Units

Weight (kg)

Height (cm)

Body Composition Analysis

Formula	Lean Mass (LBM)	Fat Mass	Body Fat %
Boer Formula (1984)	58.0 kg (128.0 lbs)	17.0 kg (37.4 lbs)	22.6%
James Formula (1976)	59.0 kg (130.1 lbs)	16.0 kg (35.3 lbs)	21.3%
Hume Formula (1966)	54.4 kg (120.0 lbs)	20.6 kg (45.3 lbs)	27.4%

Body Mass Breakdown

Lean: 76.2%Fat: 23.8%

Daily Protein Recommendations

101g - 151g

Based on an active guideline of 0.8g to 1.2g of protein per pound of lean body mass. Adjust according to training density.

LBM Formulas: The Boer, James, and Hume algorithms calculate target fat-free limits using height-weight regression matrices.

Understanding Lean Body Mass benchmarks

Lean body mass represents the weight of muscles, bones, ligaments, tendons, organs, and water — everything in the body except stored fat.

Tracking body composition is key for strength athletes. Protein intake calculations leverage lean mass metrics to prevent muscle breakdown.

Built and maintained by Meet Shah · Last updated 1 August 2026

What this tool is used for

Estimating lean mass to set a protein target from it rather than total weight.
Comparing the Boer, James and Hume formulas on the same measurements.
Getting a fat-mass figure alongside the lean estimate.
Tracking a change in composition rather than in weight alone.
Producing a figure to discuss with a coach.

Frequently Asked Questions

What counts as lean body mass?: Everything that is not fat: muscle, bone, organs, connective tissue and water. It is roughly 60–90% of total mass depending on body fat, and it is the figure that matters for protein targets and for drug dosing, because fat tissue is not metabolically comparable.
How is it estimated without a body composition scan?: Either from a body fat percentage — LBM = weight × (1 − BF%) — or from a regression formula on height and weight such as Boer or James. The first is exact given an accurate BF%; the second is a population estimate that cannot know how muscular you are.
Which formula should I use?: Boer is the usual default and performs well across a normal range. Hume and James diverge more at the extremes. If you have a reliable body fat measurement from DEXA or a good caliper protocol, use that path instead — every regression formula is trying to approximate the number you already have.
Why does LBM matter for protein intake?: Because protein requirements track muscle mass, not total weight. Prescribing grams per kilogram of body weight overshoots substantially for someone carrying high body fat, which is why the recommendation shown here is derived from lean mass — around 1.0 to 1.2 grams per pound of LBM.
Can lean body mass change quickly?: Not the muscle part. A large short-term move is almost always water and glycogen — a low-carbohydrate week can drop several pounds of LBM on a scale reading with no muscle lost at all. Real muscle gain is measured in pounds per month at best, even when training is ideal.

Common errors and gotchas

Comparing figures from different formulas, which are not interchangeable and can differ by kilograms.
Treating a formula estimate as a measurement, where only imaging or a proper scan measures composition.
Using it at the extremes of height or weight, where the formulas were not validated.
Mixing units between height and weight, which the formulas cannot detect.
Reading the number as a health assessment on its own.