What is lean body mass?

Everything in your body that is not fat — muscle, bone, organs and water. It equals your weight minus your fat mass.

How is lean body mass calculated?

This uses the Boer formula, which estimates it from your weight, height and sex. Fat mass is your weight minus that figure.

Is this the same as muscle mass?

No. Muscle is part of lean mass, but lean mass also includes bone, organs and water. It overestimates muscle alone.

How accurate is the estimate?

It is a population formula. For a real measurement, a DEXA scan or bioelectrical impedance is more precise.

Health & Fitness

Lean Body Mass Calculator

Lean body mass is everything that is not fat — muscle, bone, organs and water. It matters for dosing, nutrition and tracking muscle. This estimates it from your height, weight and sex with the Boer formula.

Your numbers

Result

Lean body mass

60.89

Fat masskg: 19.11
Lean mass share% of body weight: 76.11

Body composition (Boer formula)
Item	Value
Lean body mass (kg)	60.9
Fat mass (kg)	19.1
Lean mass share	76.1%

How it is estimated

The Boer formula predicts lean mass from weight and height. For men: LBM = 0.407 x weight(kg) + 0.267 x height(cm) - 19.2; for women: LBM = 0.252 x weight + 0.473 x height - 48.3. Your fat mass is simply your weight minus the lean mass. It is an estimate, not a measurement.

Why lean mass matters

Lean mass drives your metabolic rate and strength, and some medication doses are based on it rather than total weight. Losing weight while keeping lean mass (through protein and resistance training) is the goal for most people — you want the fat to go, not the muscle.

Informational and educational result. Not a substitute for professional advice.

Frequently asked questions

Sources

Boer P (1984) — lean body mass from height and weight

Embed this calculator

Copy the code and paste it into your site or blog. Credit with a link back to Contania is included, and the height adjusts itself.

<iframe src="https://contania.app/embed/health/lean-body-mass" title="Lean Body Mass Calculator (Boer formula)" width="100%" height="720" loading="lazy" style="border:1px solid #e5e0d8;border-radius:12px;max-width:640px"></iframe>
<script>window.addEventListener("message",function(e){if(e.data&&e.data.type==="contania:embed-height"){var f=document.querySelector('iframe[src="https://contania.app/embed/health/lean-body-mass"]');if(f){f.style.height=e.data.height+"px"}}});</script>

Related calculators