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Body Fat Calculator
Estimate body-fat percentage with the US Navy method.
100% FreeRuns instantlyNo watermark
- 1Enter detailsAdd the numbers for your scenario.
- 2CalculateVootkit updates the result instantly.
- 3ReviewCheck totals, notes and breakdowns.
Private by designProcessed on your device where possible.
Works on any deviceDesktop, tablet and mobile browsers.
No installationOpen the page and start working.
Always free coreUse the free plan for everyday tasks.
How to use Body Fat Calculator
Vootkit updates the result instantly.
02Check totals, notes and breakdowns.
03Copy the answer into your workflow.
04Your files stay private
Your work is processed locally in your browser where possible and is never added to a Vootkit upload library.
Learn more about privacyWeight alone cannot tell muscle from fat, which is why two people of identical height and weight can be in visibly different condition. A tape measure gets closer than a scale does — though it is still an estimate, and a fairly rough one.
What Body Fat Calculator does
Uses the US Navy circumference method, which estimates body fat from neck, waist and height (plus hip for women) via a logarithmic formula. For men: 495 / (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450.
Requires only a tape measure, which is why it is used where calipers or scanners are impractical. It infers fat distribution from a few circumferences rather than measuring anything directly.
Method and measurements
| Method | US Navy circumference (Hodgdon-Beckett) |
|---|---|
| Men need | Height, neck, waist |
| Women need | Height, neck, waist, hip |
| Units | Centimetres |
| Typical accuracy | ±3–4 percentage points vs DEXA |
| Neck measured at | Just below the larynx |
| Waist measured at | Navel, relaxed — not held in |
| Hip measured at | The widest point |
Detailed steps
- Measure with a soft tape, snug but not compressing the skin.
- Take the waist at the navel while breathing out normally — do not hold it in.
- Enter the measurements and read the estimate.
Worth knowing
Measurement error dominates this result. A centimetre of difference at the waist can move the answer by more than a percentage point, so measure three times and use the middle value — and always at the same time of day, since waist circumference varies noticeably between morning and evening.
Frequently Asked Questions
How accurate is this really?
Within about 3–4 percentage points of a DEXA scan for most people, which is useful for tracking a trend and poor for a single verdict. It is least accurate at the extremes — very lean and very heavy bodies both tend to be misestimated.
Why does it need my neck?
The neck acts as a proxy for frame size, letting the formula separate build from fat. Without it, a naturally broad person and a heavier person of the same waist would score the same.
Why do women need a hip measurement?
Because typical fat distribution differs, and the female version of the formula uses waist plus hip minus neck to account for it. Using the male formula on a female body gives a meaningfully wrong answer.
It disagrees with my smart scale.
Both are estimates using entirely different assumptions — this one from circumferences, the scale from electrical impedance, which is sensitive to hydration and even to how recently you ate. Neither is ground truth. Pick one method and follow its trend rather than comparing across them.
Is Body Fat Calculator free?
Yes. The Vootkit free plan includes 5 tool runs a day. Upgrade to Vootkit Pro for unlimited daily use, an ad-free workspace and saved workflows.
Are my files uploaded?
No. Body Fat Calculator runs entirely in your browser — your file is processed on your own device and never sent to a server. There is nothing for us to store or delete.
Do I need to install anything?
No. Body Fat Calculator works in any modern browser on desktop, tablet or phone. Open the page and start.
How often can I use it? Is there a daily limit?
On the free plan you get 5 tool runs a day. When you reach the limit you'll see a prompt to upgrade, and it resets the next day. Vootkit Pro removes the cap entirely for unlimited daily use.
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This tool processes everything locally in your browser. You can disconnect from the internet after the page loads and it will still work.