Body Fat Calculator Calculators
Estimate body fat percentage using the US Navy tape method.
Body Fat Calculator is a free online tool that estimate body fat percentage using the US Navy tape method. It runs entirely in your web browser using plain JavaScript, so files are processed on your own device and never uploaded to a server. There is no sign-up, no file size limit imposed by the site, no watermark and no paid tier.
- Price
- Free — no account, no quota, no watermark
- Category
- Calculators
- Where it runs
- In your browser, on your device
- Files uploaded
- None
- Technology
- plain JavaScript
- Settings
- 6
- Works offline
- Yes, after the first visit
About Body Fat Calculator
The US Navy tape method estimates body fat from circumference measurements and height, using a logarithmic regression fitted in the 1980s. It is free and repeatable, with a typical error of 3–4 percentage points against DEXA — good enough to track direction, not good enough to argue about a single reading.
How to use it
- Enter sex at birth, height (cm) and neck (cm).
- Adjust the remaining 3 settings if the defaults do not fit your case.
The 6 settings
| Setting | What it does | Default |
|---|---|---|
| Sex at birth | Choose from 2: Female, Male. | Female |
| Height (cm) | A numeric value. | 170 |
| Neck (cm) | A numeric value. | 34 |
| Waist (cm) | A numeric value. | 80 |
| Hip (cm) — female only | A numeric value. | 95 |
| Weight (kg) | A numeric value. | 70 |
Under the hood
| Runs on | plain JavaScript — runs the whole thing |
| Controls | Sex at birth, Height (cm), Neck (cm), Waist (cm), Hip (cm) — female only, Weight (kg) |
Questions
How should I take the measurements?
Relaxed, at the end of a normal exhale, tape snug but not compressing. Waist at the navel for men, at the narrowest point for women. Measure at the same time of day each time — consistency matters more than absolute accuracy.
Is the arithmetic exact?
It uses double-precision floating point — about 15 significant figures, far more than the inputs justify. Displayed rounding is cosmetic; the underlying numbers are not rounded between steps, so chained results do not drift.