Fat Mass Calculator
From total weight and body fat percentage, get total fat mass and lean mass split into kilograms.
Scan to open on your phone
Point your phone camera at the code to open this tool.
From total weight and body fat percentage, get total fat mass and lean mass split into kilograms.
How to use Fat Mass Calculator
- Open the toolNo signup and nothing to install; it works as soon as the page loads.
- Set “Weight (kg)”
- Set “Body fat %”
- Read the resultChange any input and the result is recalculated immediately.
Worked example with the defaults
- FAT MASS · Based on 20% body fat
- 14.0 kg
Nothing you enter leaves your device
All of the work happens inside your browser. Whatever you type is never packaged up and sent to a server, and no request this page makes carries it.
That makes it safe for contract amounts, personal details and internal documents you would rather not hand to a third party — close the tab and it is gone.
What this tool does not do
Fat Mass Calculator only does what a browser can do on its own — it talks to no backend service. So it keeps no history for you and syncs nothing across devices; if you need a record, copy or download the result.
It is also not a substitute for professional judgement. For legal, medical or tax decisions, treat the output as a starting point rather than a final answer.
Frequently Asked Questions
- Body fat from where?
- DEXA, calipers, BIA scales — all are estimates. The percentages differ, so re-measure with the same method and look at trends, not absolute numbers.