Body Fat Percentage Calculator (Navy Method)
Enter a few tape-measure girths and this calculator estimates your body fat percentage using the US Navy circumference method, then classifies the result against standard American Council on Exercise ranges and, if you add your weight, splits it into fat mass and lean mass. It is a low-cost estimate you can repeat at home to track a trend over time — not a clinical measurement, and no substitute for DEXA, hydrostatic weighing, or a doctor's assessment.
Estimated body fat
18.4%
ACE category: Average
You vs healthy-range markers
Inputs & result detail
Estimate only. The Navy tape method is a population formula, not a body-composition measurement like DEXA. It is not medical advice — see a clinician or dietitian for an assessment.
Compare scenarios
Run the same calculation with two or three input sets side by side. Differences are highlighted; every number comes from the same tested formula as the calculator above.
| Input | Scenario A | Scenario B |
|---|---|---|
| Sex | ||
| Waist Cm | ||
| Neck Cm | ||
| Hip Cm | ||
| Height Cm | ||
| Weight Kg |
How it works
The US Navy method fits body fat to a few circumferences and your height. For men it uses waist minus neck; for women it uses waist plus hip minus neck, because female fat distribution differs. Those girths and your height go through a base-10 logarithmic formula (a regression fitted against hydrostatic-weighing data) to produce a single body-fat percentage — no calipers or lab equipment required, just a flexible tape.
Your result is placed into the ACE body-composition bands for your sex — Essential, Athlete, Fitness, Average, and Obese — so you can see where the estimate falls rather than reading a bare number. If you enter your body weight, the tool multiplies it by the body-fat percentage to give fat mass, and the remainder is your fat-free (lean) mass, which includes muscle, bone, organs, and water.
Because the whole estimate rides on a handful of tape measurements, technique matters more than the decimal places: measure the waist at the navel, the neck just below the larynx, and the hip at its widest, keeping the tape snug, level, and not compressing the skin. Measure at the same time of day under the same conditions and average two or three readings — a centimetre of difference at the waist visibly shifts the percentage.
Frequently asked questions
How accurate is the Navy tape method versus a DEXA scan?+
The Navy circumference formula is a population regression, so it estimates the average body fat for people with your girths and height — an individual can land several points off. Reference methods such as DEXA, hydrostatic (underwater) weighing, and air-displacement plethysmography are far more precise because they physically measure body composition rather than inferring it from a tape. The tape method's real strength is that it is free, repeatable, and consistent, which makes it good for tracking change over weeks and months. Treat the single number as a ballpark and the trend as the signal.
Why do my measurements matter so much, and how do I take them right?+
Every input feeds a logarithm, so small tape errors move the result more than you would expect. Use a flexible (cloth or fibreglass) tape, keep it horizontal and snug without denting the skin, and relax rather than sucking in. Measure the waist at the navel, the neck just under the Adam's apple angled slightly down at the front, and — for women — the hip at the widest point of the buttocks. Take each measurement two or three times and average them, and always measure under the same conditions (for example, first thing in the morning) so your comparisons over time are fair.
Is this body fat percentage medical advice?+
No. This tool is for general education and self-tracking only and is not medical advice, diagnosis, or treatment. Body fat percentage is just one crude signal of health, and healthy ranges vary with age, ethnicity, athletic background, and individual physiology. Do not use this estimate to justify extreme dieting or to self-diagnose. If you have concerns about your weight, body composition, or health, talk to a physician or a registered dietitian who can assess you properly.