Body Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy circumference method — just a tape measure, no calipers or scan required. Metric or imperial.
How to use
Where exactly to measure
Waist: wrap the tape horizontally around your body at the level of your navel, not at the narrowest point of your torso — this matters because the Navy formula was validated using the navel landmark specifically. Neck: measure just below the larynx (Adam's apple), with the tape sloping slightly downward at the front, similar to where a collar would sit. Hip (women only): measure at the widest part of the hips and buttocks, standing with feet together. In each case keep the tape parallel to the floor, wrapped snug against the skin but not pulled tight enough to compress it, and take the reading after a normal exhale rather than sucking in or pushing out your stomach.
Why body fat % beats BMI alone
BMI only uses height and weight, so it cannot distinguish muscle from fat — see our BMI Calculator for that formula and its categories. Two people with identical height, weight and therefore identical BMI can have very different body compositions: a muscular, lean athlete and someone carrying more fat but less muscle can register exactly the same BMI number, even though their health profiles differ substantially. Body fat percentage measures composition directly rather than mass relative to height, which is usually the more informative figure for tracking real fitness or health changes over time, especially during strength training when muscle gain can mask fat loss on the scale.
Margin of error to expect
Studies comparing the Navy circumference method against DEXA (dual-energy X-ray absorptiometry) scans — a clinical gold-standard for body composition — typically find agreement within about ±3-4% body fat when measurements are taken correctly by an experienced measurer. That margin widens noticeably if the tape is placed at the wrong landmark, pulled too tight or too loose, or if the reading is taken right after a large meal or intense exercise when the body is swollen or dehydrated. Treat the result this tool gives you as a solid estimate for tracking trends over weeks and months, not as a lab-grade, one-off number.
Getting consistent, comparable readings
If you want to track change over time, measure at the same time of day (first thing in the morning, before eating or drinking, works well), using the same tape measure, and the same exact spots each time. Small differences in tape placement between sessions can shift the result by a percentage point or two even though your actual body composition hasn't changed — consistency in technique matters more than any single reading.
The U.S. Navy circumference method was developed in the 1980s by researchers Hodgdon and Beckett as a fast, low-cost way to estimate sailors' body composition for fitness standards without needing hydrostatic weighing or calipers. It has since become one of the most widely used tape-measure formulas because it needs no special equipment and correlates reasonably well with more precise clinical methods.
Frequently asked questions
How accurate is the Navy method?
The U.S. Navy circumference method is typically cited as accurate to within about ±3-4% body fat compared to lab methods like DEXA scans, provided measurements are taken carefully with a proper technique at the correct landmarks. It is far more accurate than BMI alone for estimating body composition, since it directly measures circumferences that correlate with fat distribution rather than just overall mass relative to height. That said, it is still an estimate derived from a population-level formula, not a diagnostic measurement, and individual results can vary more or less depending on body shape and where you personally tend to carry fat.
What's a healthy body fat percentage?
Using the American Council on Exercise (ACE) categories, an "acceptable" range is roughly 18-24% for men and 25-31% for women, with "fitness" level sitting a little lower again (14-17% for men, 21-24% for women). Athletes typically sit lower still (6-13% for men, 14-20% for women), while essential fat is the bare minimum needed for basic physiological function like hormone production and organ protection (2-5% for men, 10-13% for women) — going below essential fat levels is not healthy. What counts as "healthy" also varies with age, genetics and individual circumstances, so these ranges are general guidance rather than strict cutoffs.
Why does the formula ask for hip measurement for women but not men?
Men and women tend to store fat in different patterns on average — men more centrally around the abdomen ("apple" shape), women more around the hips and thighs ("pear" shape), largely due to hormonal differences. The Navy method's female formula includes hip circumference specifically to account for this typical distribution pattern, while the male formula relies on waist and neck circumference alone because the abdominal measurement already captures most of the relevant variation for men. This is a population-level statistical adjustment built into the original research, not a claim about any individual person's shape.
How is this different from BMI?
BMI only uses height and weight, so it cannot distinguish muscle from fat — a muscular athlete and a sedentary person of the same height and weight can have very different body fat percentages but identical BMI, because BMI has no way to "see" body composition. The Navy method uses body circumference measurements instead, giving a more direct estimate of how much of your body is fat versus lean tissue, rather than just overall mass relative to height. Neither replaces the other entirely — BMI is a quick population-screening tool, while a circumference method like this one gets closer to actual composition. See our BMI Calculator to compare both for yourself.