Lean Body Mass Calculator
Estimate your lean body mass with the Boer, James and Hume formulas, plus your implied body fat percentage and category. Metric or imperial, instant and private.
Input
Output
| Measure | Kilograms | Pounds |
|---|---|---|
| No data yet | ||
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/lean-body-mass-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"units": "metric",
"sex": "male",
"weight": "75",
"height": "178"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `lean-body-mass-calculator` tool (Lean Body Mass Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/lean-body-mass-calculator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="Lean Body Mass Calculator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
Also available with
Guides
Lean body mass (LBM) is everything in your body that isn't fat: muscle, bone, organs and water. This calculator estimates it with three well-known formulas, then derives your fat mass and body fat percentage. It runs entirely in your browser.
The three formulas
Weight is in kilograms and height in centimetres (imperial input is converted for you).
- Boer — men:
0.407 × W + 0.267 × H − 19.2; women:0.252 × W + 0.473 × H − 48.3. - James — men:
1.1 × W − 128 × (W / H)²; women:1.07 × W − 148 × (W / H)². - Hume — men:
0.3281 × W + 0.33929 × H − 29.5336; women:0.29569 × W + 0.41813 × H − 43.2933.
The tool shows each result and their average. Estimated body fat is (weight − average LBM) ÷ weight, and is placed in an ACE category (essential fat, athletes, fitness, average, above average).
How accurate is it?
These are population-level equations, not measurements. They tend to agree within a few kilograms for average builds, but they can't see how muscular you are. For a precise figure use DEXA or a similar scan. They are best used to track trends over time.
Why it matters
LBM drives your resting metabolism and is the basis for many protein and drug-dosing calculations. Pair it with the Protein Intake Calculator to set a daily protein target.
FAQ
Which formula should I trust? Use the average; the three differ mainly at the extremes of height and weight.
Is my data stored? No. All calculation happens on your device.