Enter your sex, height, and neck / waist (and hip, for women) measurements - the estimate updates as you type. Pick metric (cm) or imperial (in) units first, then measure with a soft tape at the narrowest point of the neck and waist for the most consistent reading. The tool computes the U.S. Navy circumference-method estimate and a fitness category entirely in your browser - nothing is uploaded.
Body Fat Percentage Calculator Online
Estimate body fat percentage from a few tape-measure numbers using the U.S. Navy circumference method, right in your browser.
Key features
- Uses the U.S. Navy circumference method: height, neck, and waist for men; height, neck, waist, and hip for women.
- Switch between metric (cm) and imperial (in) units at any time; the result and its fitness category update as you type.
- Shows a fitness category alongside the number: essential fat, athletic, fitness, average, or above average, by sex.
Estimate vs precise measurement
It is an estimate, not a medical measurement. For a more precise reading, use one of the methods below.
| Method | Precision |
|---|---|
| This calculator (Navy circumference formula) | Estimate from tape-measure numbers |
| DEXA scan | More precise |
| Bioelectrical-impedance scale | More precise |
| Skinfold calipers | More precise |
What each fitness category means
The calculator labels the estimate with one of five categories, and men and women sit on different cutoffs - the same number means a different category depending on the sex selected.
| Category | Men | Women |
|---|---|---|
| Essential fat | Below 6% | Below 14% |
| Athletic | 6% to 13.9% | 14% to 20.9% |
| Fitness | 14% to 17.9% | 21% to 24.9% |
| Average | 18% to 24.9% | 25% to 31.9% |
| Above average | 25% and up | 32% and up |
A waist bigger than the neck can still show an error
The error message asks for measurements greater than zero, but the underlying formula needs more than just waist exceeding neck - it needs a real gap between the two, and taller measurements need a wider gap. At the calculator's own metric defaults (height 175cm, neck 38cm), a waist of 58cm - a 20cm gap - still returns the error, because the formula's result is below zero at that gap. The gap has to widen to roughly 30cm (a waist around 68cm) before the estimate turns positive, and from there it climbs steadily: the same 38cm neck with an 85cm waist (a 47cm gap) works out to about 17%, in the Fitness band. Height moves that floor - the same 32cm gap that is already positive at 175cm tall is still slightly negative at 200cm tall.
The estimate is held between 2% and 60%
Every result, once it clears zero, is capped at both ends. An unusually large waist-to-neck gap does not push the displayed number past 60%, and a gap that only just clears zero shows as 2% rather than a fraction of a percent.
Privacy
Your tape-measure figures stay in the browser - the estimate is worked out on this device, with no upload and no account.
Frequently Asked Questions
What does Body Fat Percentage Calculator Online do?
It estimates your body fat percentage from height, neck, and waist measurements (plus hip for women) using the U.S. Navy circumference method, and shows a fitness category alongside the number.
How accurate is the U.S. Navy circumference method?
It is a widely used estimate, typically within a few percentage points of more precise methods like DEXA scans or skinfold calipers - close enough to track trends over time, but not a medical measurement.
Do I need to sign up or upload anything?
No. Every calculation runs locally in your browser; no account, no upload, and your measurements never leave the page.
My waist is bigger than my neck - why does it still say to enter measurements greater than zero?
The formula needs a real gap between the two, not just any positive difference, and how large that gap needs to be depends on your height. At the calculator's own defaults (height 175cm, neck 38cm), a 20cm gap still returns the error; the gap needs to reach roughly 30cm before the estimate turns positive. Re-measure both figures, or try a slightly larger waist value, if you see this message.
What are the exact percentage ranges behind each category?
Men: Essential fat below 6%, Athletic 6% to 13.9%, Fitness 14% to 17.9%, Average 18% to 24.9%, Above average from 25%. Women: Essential fat below 14%, Athletic 14% to 20.9%, Fitness 21% to 24.9%, Average 25% to 31.9%, Above average from 32%.
Can the result show 0% or a number over 60%?
No. Once the formula clears zero, the displayed estimate is held between 2% and 60% regardless of how extreme the measurements are - an unusually wide waist-to-neck gap still shows 60% at most, and a gap that only just clears zero shows 2% rather than a smaller fraction.