Lean Body Mass Calculator
Estimate your lean body mass, fat mass and lean percentage from your weight and height using the Boer formula.
What is lean body mass?
Lean body mass is everything in your body that is not fat. It includes muscle, bone, organs, blood and the water held inside them. Because it covers so much, it is far more than just the muscle you can flex. This calculator estimates your lean body mass with the Boer formula, a widely used equation that takes your weight, height and sex into account. Once it has your lean mass, it also works out your body fat percentage — the share of your weight that is fat — and your fat mass in kilograms. The distinction matters because the scale alone cannot tell you whether a change in weight came from fat, muscle or water. Two people can weigh the same and have very different bodies, and lean mass is a big part of the reason. This tool is a quick, equipment-free estimate that runs entirely in your browser. It gives you a useful reference for tracking progress or setting a body-composition goal, though it is an estimate rather than a clinical measurement.
Example
Select Male and enter a weight of 80 kg and a height of 180 cm. The tool returns a lean body mass of about 61.4 kg — 0.407 × 80 + 0.267 × 180 − 19.2. That comes with a fat mass of about 18.6 kg and a body fat percentage of about 23.2%.
Who is this lean body mass calculator for?
This lean body mass calculator estimates your non-fat mass from weight and height using the Boer formula. It is a quick reference for anyone who wants a better picture of body composition than the scale gives them.
- Fitness and athletes: Athletes and lifters use a lean body mass calculator to gauge how much muscle they carry and to track gains, since weight alone can hide muscle growth.
- Weight loss: When you lose weight, this tool helps show whether the loss is coming from fat or from lean mass, which is a key concern on any cutting plan.
- Body composition: If you are monitoring body composition, lean mass and body fat percentage together tell you far more than BMI, which ignores fat versus muscle.
- Trainers and coaches: Personal trainers use a lean body mass result to set sensible targets and to show clients that two equal-weight people can need very different plans.
Lean body mass chart and table — Boer formula by weight
These lean body mass values are worked out with the same Boer formula as this calculator, for a fixed height and a range of weights. They are general estimates, not a health assessment.
| Reference | Weight | Lean body mass | Fat mass | Body fat % |
|---|---|---|---|---|
| Men (180 cm) | 70 kg | 57.3 kg | 12.7 kg | 18.1% |
| Men (180 cm) | 80 kg | 61.4 kg | 18.6 kg | 23.2% |
| Men (180 cm) | 90 kg | 65.5 kg | 24.5 kg | 27.2% |
| Men (180 cm) | 100 kg | 69.6 kg | 30.4 kg | 30.4% |
| Women (165 cm) | 50 kg | 42.3 kg | 7.7 kg | 15.3% |
| Women (165 cm) | 60 kg | 44.9 kg | 15.1 kg | 25.2% |
| Women (165 cm) | 70 kg | 47.4 kg | 22.6 kg | 32.3% |
| Women (165 cm) | 80 kg | 49.9 kg | 30.1 kg | 37.6% |
Common use cases
- Tracking whether a weight change is fat loss or lean-mass loss while dieting.
- Setting a realistic muscle-building target and measuring progress over months.
- Getting a starting point for body composition when you have no testing equipment.
- Comparing lean mass with BMI to understand your overall composition better.
Pro tips
- Weigh yourself at the same time of day on the same scale, ideally in the morning, for a consistent trend.
- Treat the estimate as a trend rather than a single number, since the Boer formula is population-based, not a measurement.
- Pair this with waist or body-fat tape measurements for a fuller picture than either gives alone.
- Recall that lean mass naturally declines a little with age, so a small change is not always a sign of losing muscle.
How to use this lean body mass calculator
- Select your sex.
- Enter your weight in kilograms and your height in centimetres.
- Click Calculate lean body mass to see your lean mass, fat mass and lean percentage.
The calculator works in metric units. To convert to imperial use 1 kg = 2.20462 lb and 1 cm = 0.3937 in.
How lean body mass is calculated
Men: LBM = 0.407 × weight + 0.267 × height − 19.2 Women: LBM = 0.252 × weight + 0.473 × height − 48.3 Body fat % = (weight − LBM) / weight × 100 Fat mass = weight − LBM
The Boer formula uses weight in kilograms and height in centimetres. Once lean body mass is found, body fat percentage is the portion of weight that is not lean mass, and fat mass is the rest. Lean percentage is simply body fat percentage subtracted from 100.
FAQ
What is lean body mass?
Lean body mass is everything in your body except fat — muscle, bone, organs, water and connective tissue. It is your total weight minus your fat mass.
Which formula does this calculator use?
It uses the Boer formula, which estimates lean body mass from weight, height and sex and is widely used in clinical and fitness settings.
How is lean body mass calculated?
For men LBM = 0.407 × weight + 0.267 × height − 19.2; for women 0.252 × weight + 0.473 × height − 48.3, with weight in kg and height in cm.
What is a healthy lean body mass percentage?
There is no single target; it varies by sex, age and frame. Most men carry roughly 75–85% lean mass and women about 70–80%, but athletes can be higher.
What is body fat percentage?
Body fat percentage is your fat mass divided by total weight, multiplied by 100. This calculator derives it from your lean mass.
How accurate is the Boer formula?
It is a good estimate for the general population, but it is not a measurement, so treat it as a reference rather than a precise value.
Is it private?
Yes — the calculation runs entirely in your browser and nothing is sent to a server.
Is lean body mass the same as muscle mass?
No. Lean body mass includes muscle plus bone, organs, water and other non-fat tissue, so it is always larger than pure muscle.
Why do men and women get different results?
The Boer formula uses separate coefficients because women naturally carry a higher share of essential fat, so the same weight and height yield a lower lean estimate.
Should I use this or BMI?
Use both. BMI compares weight to height, while lean body mass separates fat from non-fat tissue, giving a clearer picture of composition.
Does it capture body fat directly?
No. It estimates lean mass first, then derives body fat percentage as (weight − lean mass) divided by weight. It is context, not a direct measurement.
What units does it work in?
It uses kilograms and centimetres. To convert to imperial: 1 kg = 2.20462 lb and 1 cm = 0.3937 in.
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