# Free online lean body mass calculator

> Lean body mass is total body weight minus fat mass. This calculator uses three validated clinical formulas to estimate LBM from weight and height.

Estimate your lean body mass (LBM) using the Boer, James, and Hume formulas. Optionally enter body fat percentage for a direct measurement.

**Interactive version:** https://onlinecalculator.me/health/lean-body-mass/
**Category:** Health

## How to use

1. Select your **biological sex**.
2. Enter your **weight** in pounds and **height** in inches.
3. Optionally enter your **body fat percentage** for a direct LBM calculation.
4. Click **Calculate LBM**.
5. See results from three formulas compared side by side.

## Formulas

**Boer (1984) — default:**
- Male: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2
- Female: LBM = 0.252 × weight(kg) + 0.473 × height(cm) − 48.3

**James (1976):**
- Male: LBM = 1.1 × weight(kg) − 128 × (weight/height)²
- Female: LBM = 1.07 × weight(kg) − 148 × (weight/height)²

**Hume (1966):**
- Male: LBM = 0.3281 × weight(kg) + 0.3393 × height(cm) − 29.53
- Female: LBM = 0.2957 × weight(kg) + 0.4181 × height(cm) − 43.29

**From body fat %:**
- LBM = Total weight × (1 − body fat% / 100)

## Worked example

**170 lb (77.1 kg) male, 5′10″ (177.8 cm):**

Boer LBM = 0.407 × 77.1 + 0.267 × 177.8 − 19.2 = 31.4 + 47.5 − 19.2 ≈ **59.7 kg (131.6 lbs)**

## Frequently asked questions

### What is lean body mass?

Lean body mass (LBM) is everything in your body that isn't fat — muscle, bone, water, organs, and connective tissue. It is the metabolically active portion of body mass.

### Which formula is most accurate?

The Boer formula (1984) is generally considered the most accurate for clinical use. The three formulas give similar results for people of average build, but differ more at extreme heights and weights.

### How is LBM different from muscle mass?

Lean body mass includes all non-fat tissue — muscle, bone, organs, and water. Muscle mass is just one component of LBM. They are not interchangeable terms.

### What is a healthy LBM?

There is no universal healthy LBM, as it depends on total body weight, height, sex, and goals. Athletes typically have higher LBM relative to body weight. LBM is useful for tracking changes over time.

### Why does sex affect LBM?

Males generally have more muscle mass and denser bones than females at the same height and weight, resulting in higher LBM. The formulas use sex-specific coefficients to account for this.

## Sources

- [Estimated lean body mass as an index for normalization of body fluid volumes](https://doi.org/10.1152/ajprenal.1984.247.4.F632) — American Journal of Physiology

## Related calculators

- [Body fat percentage calculator](https://onlinecalculator.me/health/body-fat/) — Estimate body fat using the US Navy tape method.
- [BMI calculator](https://onlinecalculator.me/health/bmi/) — Calculate body mass index from height and weight.
- [Ideal weight calculator](https://onlinecalculator.me/health/ideal-weight/) — Find your ideal weight using multiple formulas.
- [Macro calculator](https://onlinecalculator.me/health/macros/) — Calculate daily protein, fat, and carbohydrate targets.

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