Body Fat Percentage Calculator
This calculator uses the US Navy circumference method, which estimates body fat percentage from your height, neck and waist — plus hip measurement for women. All you need is a tape measure. Enter your measurements below and you'll get an estimated body fat percentage, along with how much of your weight is fat and how much is lean tissue.
Enter your height, neck and waist measurements to estimate body fat.
Body fat percentage tells you something BMI cannot: what your weight is actually made of. Two people at the same height and weight can have very different amounts of muscle and fat, and only one of those numbers changes the picture. The trade-off is that body fat is much harder to measure accurately than weight, and every practical method is an estimate.
How the tape method works
The US Navy method — properly the Hodgdon-Beckett equation — was developed as a practical body composition screen for large numbers of people without laboratory equipment. It works because fat distributes in reasonably predictable patterns: waist girth relative to neck girth, scaled by height, correlates well enough with total body fat to be useful.
For men the inputs are height, neck and waist. For women, hip circumference is added, because fat distribution differs enough between sexes that the male equation would systematically misread a female body. The equations are logarithmic rather than linear, which is why the constants look arbitrary.
Notably, body weight is not an input. The estimate comes purely from shape. Your weight is used here only afterwards, to convert the percentage into kilograms of fat and lean tissue.
How to measure properly
Measurement error is by far the largest source of error in this method. A centimetre of slack at the waist can shift the result by more than a percentage point, so it is worth doing carefully rather than quickly.
- NeckJust below the larynx, with the tape sloping slightly downward at the front. Keep your shoulders relaxed and do not flex.
- Waist (men)At the navel, horizontal all the way round. Do not pull the tape tight and do not suck in.
- Waist (women)At the narrowest point of the torso, usually just above the navel.
- Hips (women)At the widest point of the buttocks, tape horizontal.
- GeneralMeasure at the end of a normal breath out, tape snug but not compressing the skin. Take each measurement three times and use the average.
How accurate is it?
Reasonably, for what it costs. Circumference-based estimates typically land within a few percentage points of a DEXA scan for most people, which is enough to place you in a range and — more usefully — to track change over time.
It is less reliable at the extremes. Very lean people, very heavy people, and people whose fat distribution is unusual for their sex all tend to be misread, because the equation assumes a typical distribution pattern. Someone who carries weight predominantly on the legs rather than the abdomen will read lower than they are; someone with a naturally thick neck will also read low, since a larger neck measurement reduces the calculated result.
The honest framing is that this method is better at detecting change than at establishing an absolute truth. If you measure the same way each time, a drop from 24 to 21 percent over three months is meaningful even if both numbers are a point or two off. Chasing the absolute figure to a decimal place is not what this tool is for.
If you need a genuinely accurate number — for medical reasons, or because you are competing — DEXA, hydrostatic weighing and air displacement plethysmography are the reference methods, and all of them require a facility and a fee.
What the ranges actually mean
Body fat categories are descriptions of where populations sit, not targets to aim at. The "athletic" band describes what athletes tend to measure, largely as a consequence of training volume — it is not a level to pursue directly, and for most people it is neither necessary nor comfortable to maintain.
The essential fat category at the bottom of the scale is a floor, not a goal. Some body fat is structurally required — it is part of cell membranes, nerve tissue and hormone production. Sustained very low body fat is associated with hormonal disruption, and the threshold is meaningfully higher for women than for men.
Women carry more essential fat than men for physiological reasons, which is why every band in the table below sits several points higher. Comparing a woman's body fat percentage to a man's without adjusting for that produces a misleading conclusion.
Body fat versus BMI
BMI needs a scale and a wall. Body fat needs a tape measure and five careful minutes. The extra effort buys you the one thing BMI structurally cannot provide — a distinction between muscle and fat.
That matters most for the people BMI misclassifies. A muscular person reading as overweight on BMI will usually show a low body fat percentage, which resolves the contradiction. The reverse pattern also exists: a normal BMI with a high body fat percentage and little muscle, which BMI alone would have passed as unremarkable.
For most people the two are best read together, along with a waist measurement. If they agree, the conclusion is straightforward. If they disagree, the disagreement itself is the useful information.
Changing the number
Body fat percentage is a ratio, so it moves when either side of it changes — losing fat raises the lean proportion, and gaining muscle lowers the fat proportion even at identical weight. This is why people who start training often see the percentage fall while the scale barely moves, and why the scale alone is a poor progress measure in the first few months.
Both directions come down to energy balance plus adequate protein and resistance training. Losing fat requires eating below maintenance; retaining muscle while you do it requires enough protein and a reason for your body to keep the muscle. Neither happens quickly, and rates that sound impressive are usually measuring water.
Body fat percentage ranges
Descriptive ranges published by the American Council on Exercise. Women's bands sit higher throughout because essential fat requirements differ.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
These describe where populations sit, not where you should aim. Sustained very low body fat carries its own health costs.
Frequently asked questions
How accurate is the US Navy body fat calculator?
It typically lands within a few percentage points of a DEXA scan for people with typical fat distribution, which makes it good for tracking change and reasonable for placing yourself in a range. It is less reliable at very low or very high body fat, and measurement technique affects the result more than most people expect.
What is a healthy body fat percentage?
Broadly, the fitness and average bands — roughly 14 to 24 percent for men and 21 to 31 percent for women — cover most healthy adults. There is no single correct figure, and health outcomes depend on far more than this one number.
Why does the calculator ask women for a hip measurement?
Fat distribution differs enough between sexes that a single equation would misread one of them. The female equation includes hip circumference to account for fat carried on the hips and thighs, which the male equation does not need.
Can I use this without a tape measure?
No — the method depends entirely on circumference measurements, and estimating them by eye will produce a meaningless result. A cloth tailoring tape costs very little and is the only equipment required.
Why did my body fat go up when my weight went down?
Body fat percentage is a ratio, so losing lean tissue alongside fat can raise the percentage even as weight falls. It can also simply be measurement noise. Before drawing conclusions, re-measure carefully and look at the trend across several weeks rather than two readings.
Is body fat percentage better than BMI?
It is more informative, because it distinguishes muscle from fat, but it is also harder to measure reliably. BMI is crude and consistent; body fat is richer and noisier. Reading both together, with a waist measurement, gives a better picture than either alone.
How fast can I lower my body fat percentage?
Meaningful change takes months, not weeks. Rapid drops usually reflect water loss rather than fat loss, and aggressive deficits tend to cost muscle — which raises the percentage back up by shrinking the lean side of the ratio. A moderate deficit with adequate protein and resistance training is the approach that holds.
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Open the food trackerLast reviewed 25 August 2026. These calculators use published equations and give estimates, not measurements. This is general information, not medical advice — for decisions about your health, speak to a doctor or a registered dietitian.