# Lean Body Mass Calculator

> Estimate lean body mass from height, weight and sex with the Boer and Hume equations, or from a measured body fat percentage if you have one.

Category: Health & fitness · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/lean-body-mass-calculator

Lean body mass is everything except fat: muscle, bone, organs and water. The Boer and Hume equations estimate it from height and weight; a measured body fat percentage gives a more direct figure.

Also called: LBM calculator, Fat-free mass calculator.

## Inputs
- Sex (options: Female, Male; default male)
- Units (options: Metric (cm, kg), US (ft, in, lb); default metric)
- Height (unit cm; default 180)
- Weight (unit kg; default 80)
- Height (feet) (unit ft; default 5)
- Height (inches) (unit in; default 11; optional)
- Weight (unit lb; default 176)
- Body fat (optional) (unit %; default ; optional)

## Results
- Lean body mass (Boer)
- Lean body mass (Hume)
- Lean share of weight (Boer)
- Implied fat mass (Boer)
- From your body fat %

## Formula

```
Boer: men 0.407W + 0.267H − 19.2, women 0.252W + 0.473H − 48.3;  Hume: men 0.32810W + 0.33929H − 29.5336, women 0.29569W + 0.41813H − 43.2933;  From body fat: W × (1 − BF%)
```

Where:
- W: weight in kg
- H: height in cm
- BF%: measured body fat percentage

## Worked example
1. Boer: 0.407 × 80 + 0.267 × 180 − 19.2 = 32.56 + 48.06 − 19.2 = 61.4 kg.
2. Hume: 0.3281 × 80 + 0.33929 × 180 − 29.5336 = 26.25 + 61.07 − 29.53 = 57.8 kg.
3. Lean share (Boer) = 61.42 ÷ 80 = 76.8%, implying 18.6 kg of fat.

**Result:** A man 180 cm tall weighing 80 kg has an estimated lean body mass of about 61.4 kg (Boer) or 57.8 kg (Hume).

## What the result means

The two equations differ by a few kilograms, which shows the uncertainty of height-and-weight estimates. Lean body mass is used to scale protein targets, to dose some medicines and contrast agents, and to follow changes in muscle during training or weight loss.

## Assumptions and limits
- Adult equations; Boer (1984) and Hume (1966) were derived in adult populations.
- Weight in kg and height in cm (US inputs are converted).
- Height-and-weight equations cannot tell a muscular person from a person with more fat at the same size.
- Accuracy falls in obesity, in older adults and in children.

## Questions

### Is lean body mass the same as muscle mass?

No. It includes bone, organs, skin and body water as well as muscle, so it is always larger than muscle mass alone.

### Which result should I use?

If you have a reliable body fat measurement, the body-fat method is the most direct. Otherwise Boer is the equation most often used clinically.

## Sources
- [Wikipedia: Lean body mass (Boer and Hume equations, with primary citations)](https://en.wikipedia.org/wiki/Lean_body_mass)

## Related calculators
- [Body Fat Calculator](https://calculators.geekmidst.com/calculators/body-fat-calculator)
- [Ideal Weight Calculator](https://calculators.geekmidst.com/calculators/ideal-weight-calculator)
- [BMI Calculator](https://calculators.geekmidst.com/calculators/bmi-calculator)
- [BMR Calculator](https://calculators.geekmidst.com/calculators/bmr-calculator)

_This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health._

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/lean-body-mass-calculator