Transparent method
The formula
Worked example
Example inputs
How to interpret the result
Lean body mass moves more slowly and more meaningfully than total body weight, because weight alone can shift day to day from water and digestion while lean mass reflects a genuinely different, slower-changing quantity, muscle, bone and organ tissue rather than fat. Watching lean mass over time reveals whether weight change is actually coming from fat or from muscle, which the scale alone can't distinguish.
Before you rely on it
What to check
Compare lean mass across multiple measurements spaced weeks apart, using the same formula and conditions each time, rather than reading any single figure as a fixed benchmark.
The common error
Where people go wrong with lean body mass calculator
Reading one lean-mass estimate against a generic population benchmark. The formula's real value is in tracking an individual's own change over time, not in matching a one-size figure meant for someone else's body.
Sensitivity evidence
How weight changes the estimated lean body mass
| Weight | Estimated lean body mass | Estimated fat mass |
|---|---|---|
| 136 | 116.2 | 19.8 |
| 153 | 123.1 | 29.9 |
| 170worked example | 130 | 40 |
| 187 | 136.9 | 50.1 |
| 204 | 143.9 | 60.1 |
Every input, tested
Which input moves the estimated lean body mass most
| Input | Tested from | To | Estimated lean body mass at each end | Swing |
|---|---|---|---|---|
| Height | 62 | 76 | 119.6 to 140.5 | 20.9 (16%) |
| Weight | 153 | 187 | 123.1 to 136.9 | 13.8 (11%) |
| Sex | Male | Female | 130 to 119.1 | 10.9 (8.4%) |
Two variables at once
Estimated lean body mass by weight and height
| Weight \ Height | 55 | 69 | 83 |
|---|---|---|---|
| 136 | 95.3 | 116.2 | 137.1 |
| 153 | 102.2 | 123.1 | 144 |
| 170 | 109.1 | 130 | 151 |
| 187 | 116 | 136.9 | 157.9 |
| 204 | 122.9 | 143.9 | 164.8 |
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Sex | Male | The Boer formula uses different coefficients by sex. |
| Weight | 170 | Body weight in pounds. |
| Height | 69 | Height in inches. |
| Estimated lean body mass | 130 | |
| Estimated fat mass | 40 | |
Inputs, definitions and assumptions
Sex
The Boer formula uses different coefficients by sex.
Weight
Body weight in pounds.
Height
Height in inches.
Where the inputs come from
Enter your sex, weight and height. The Boer formula estimates lean body mass, which is everything that is not fat: muscle, bone, organs and water, from weight in kilograms and height in centimeters with different coefficients for men and women. The calculator converts from pounds and inches. Use your current measured weight, and remember that the formula does not know your training or body composition.
When the result stops applying
It gives an estimate of lean mass, not muscle alone. It is not suitable for pregnancy or certain medical conditions. Direct measurement with DEXA or bioimpedance is more precise.
What to compare it with
Compare with the body fat percentage calculator, and use the result on the protein intake and macronutrient calculators for nutrition planning. The BMR and TDEE pages estimate energy use. The one-rep max and Wilks calculators relate to strength.
People also ask
Frequently asked questions
What is lean body mass?
Your total weight minus fat mass, which includes muscle, bone, organs, connective tissue and body water, so it is everything except stored fat.
Why does lean mass matter during weight loss?
Losing muscle lowers metabolism and strength, so a plan with enough protein and resistance training aims to lose fat while keeping lean mass.
How accurate is a formula for lean mass?
It is an estimate that can be off by several pounds. DEXA scans and other clinical tools are more accurate.