Lean Body Mass Calculator Online
Estimate lean body mass and fat mass from your height, weight, and sex using the Boer formula, right in your browser. A general estimate, not medical advice.
The Lean Body Mass Calculator runs entirely in your browser. The height, weight, and results you enter never leave your device and nothing is uploaded to ArrayKit. This is a general estimate, not medical advice.
Open the Body Fat Calculator
About Lean Body Mass Calculator
Lean Body Mass Calculator estimates how much of your body weight is muscle, bone, organs, and water rather than fat, using the widely referenced Boer formula. Enter your height, weight, and sex in metric or US units and get an instant lean body mass figure in kilograms, an estimated fat mass, and lean mass as a percentage of total weight. It is useful for tracking training progress, setting a protein or calorie target, or comparing body composition changes over time without any special equipment beyond a scale and a tape measure or stadiometer. This is a general estimate from a standard formula, not a clinical body-composition test or medical advice. Everything computes locally in your browser — your measurements stay on your device.
Features
- Estimates lean body mass from height, weight, and sex
- Uses the standard Boer formula
- Switch between metric (cm/kg) and US (in/lb) units
- Shows fat mass alongside lean body mass
- Displays lean mass as a percentage of total body weight
- Copy a plain-text summary of every result with one click
- Clear error messages when a measurement is missing or unrealistic
- Runs entirely in your browser with no measurements sent anywhere
How to use the Lean Body Mass Calculator
- Select your sex and preferred unit system
- Enter your body weight
- Enter your height
- Read your lean body mass, fat mass, and lean-mass percentage, and copy the summary
Example
Input
male 80kg, 180cm
Output
Lean mass: 61.5 kg
The Boer formula turns weight, height, and sex into an estimated lean body mass.
Common errors & troubleshooting
- The Lean Body Mass Calculator shows 'Enter a weight greater than 0.' — Make sure the weight field is filled in and uses the unit shown next to it (kg for metric, lb for US).
- Result looks unrealistically high or low. — Check the unit toggle matches what you typed — entering inches while set to metric (cm) skews the estimate significantly.
- Lean mass comes out higher than total body weight. — The Boer formula can overshoot for very low weights relative to height. Double-check your height and weight are both realistic and in the same unit system.
- Fat mass looks negative or missing. — Fat mass is total weight minus lean mass, so it only appears once a valid lean body mass has been calculated for the entered height, weight, and sex.
Frequently asked questions
- What formula does the Lean Body Mass Calculator use?
- It uses the Boer formula, which estimates lean body mass from height, weight, and sex: 0.407 × weight(kg) + 0.267 × height(cm) − 19.2 for men, and 0.252 × weight(kg) + 0.473 × height(cm) − 48.3 for women.
- What is lean body mass?
- Lean body mass (LBM) is everything in your body that is not fat — muscle, bone, organs, and water. The Lean Body Mass Calculator estimates it from your height, weight, and sex, then subtracts it from total weight to estimate fat mass.
- How does the Lean Body Mass Calculator differ from a body fat calculator?
- A body fat calculator like the Navy method starts from tape measurements to estimate a body fat percentage. This calculator instead estimates lean mass directly from height and weight with the Boer formula, then derives fat mass by subtraction.
- Can I use the Lean Body Mass Calculator in pounds and inches?
- Yes. Switch the unit toggle to US units to enter weight in pounds and height in inches — the calculator converts to metric internally before applying the Boer formula.
- Are my height and weight sent anywhere?
- No. The Lean Body Mass Calculator runs entirely in your browser. The figures you type never leave your device and are not uploaded to ArrayKit.
- Is the Lean Body Mass Calculator accurate enough for medical use?
- No. It gives a general estimate from a standard formula based on height, weight, and sex. It is not a substitute for a clinical body-composition scan (like DEXA) or medical advice — talk to a healthcare professional for a precise reading.
Related tools
- Body Fat Calculator — Estimate body fat percentage with the US Navy tape measurement method.
- Ideal Weight Calculator — Estimate ideal body weight with the Devine, Robinson, Miller and Hamwi formulas.
- BMI Calculator — Calculate body mass index and see the healthy weight range for your height.
- Protein Calculator — Estimate your daily protein needs from weight and activity level.
- BMR Calculator — Estimate your basal metabolic rate — the calories your body burns at rest.
- Army Body Fat Calculator — Estimate body fat with the US Army (AR 600-9) circumference method.
All ArrayKit tools