Three tape measurements and a formula from 1984 get you within a few percentage points of a DEXA scan, close enough to track real progress over time.
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Body Fat Calculator
Estimated body fat percentage from a tape measure, using the U.S. Navy circumference method.
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How accurate is a tape-measure body fat estimate?
The U.S. Navy circumference method (Hodgdon and Beckett, 1984) is what it says: an estimate from a few tape measurements, not a body composition scan. Compared against underwater weighing and DEXA scans in validation studies, it typically runs within about 3-4 percentage points of the true figure for most people, closer for average body types, further off for very lean or very muscular ones. That's accurate enough to track your own trend over weeks and months using the same measuring technique each time, but treat any single reading as a ballpark, not a lab result. Measure at the same time of day, preferably in the morning before eating, for the most consistent comparisons over time.
Body fat calculator FAQ
How accurate is the U.S. Navy body fat method?
Validation studies against underwater weighing and DEXA scans generally put it within about 3 to 4 percentage points of the true figure for most people, closer for average builds, further off at the very lean or very muscular ends. Treat it as a trend-tracking tool, not a lab-grade measurement.
Where exactly do I measure waist, neck and hip?
Neck: just below the larynx (Adam's apple), tape sloping slightly downward at the front. Waist: at the navel for men, and at the narrowest point for women per the Navy protocol. Hip (women only): around the widest part of the hips and buttocks. Keep the tape snug but not compressing the skin.
What is a healthy body fat percentage?
Using the American Council on Exercise categories: men, 14 to 24% is the "acceptable" range and 6 to 13% is athletic; women, 25 to 31% is "acceptable" and 14 to 20% is athletic. Essential fat, the minimum needed for basic health, is around 2 to 5% for men and 10 to 13% for women.
Why does the formula need different inputs for men and women?
The Navy method uses separate regression equations by sex because body fat distribution patterns differ enough between men and women that a single formula does not fit both well, women's formula also factors in hip measurement, which the male formula does not need.
Is my data private?
Yes. Every calculation runs in your browser. Nothing you enter is sent to a server, logged, or stored.
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Getting the measurements right matters more than the formula
The U.S. Navy method’s accuracy depends entirely on measuring the same three or four spots the same way every time: neck just below the larynx, waist at the navel for men or the narrowest point for women, hip at the widest point for the female formula. A tape pulled too tight or measured at a slightly different spot from last time will move the result more than any real change in your body did, consistency between measurements matters as much as precision in any single one.
Why this beats BMI for tracking body composition
BMI can’t tell muscle from fat, this method actually estimates fat specifically, which is why two people with an identical BMI can show meaningfully different body fat percentages here. If a BMI result seemed off for your build, this is usually the more honest number, our BMI Calculator explains that specific limitation in more detail.
Treat it as a trend line, not a lab result
Validation studies put the U.S. Navy method within roughly 3 to 4 percentage points of underwater weighing or DEXA for most people. That’s accurate enough to tell whether you’re moving in the right direction over weeks and months, measured consistently, but not precise enough to treat a single reading as clinical fact. If you need a lab-grade number for a medical reason, ask about a DEXA scan.