How accurate is the US Navy method?

Studies comparing it to DEXA scans generally find it within about 3–4 percentage points for most body types — good enough to track trends, not precise enough for clinical or research use. Consistent measurement technique matters more than which formula you use.

Where exactly do I measure?

Neck: just below the larynx. Waist: at the navel for men, at the narrowest point for women (per the original Navy protocol). Hip (women only): at the widest point of the hips/glutes. Measure snug but not compressed, and take the average of two readings.

Why does the female formula need a hip measurement but the male one doesn't?

The original 1984 Navy study (Hodgdon & Beckett) found that fat distribution differences between sexes meant hip circumference improved prediction accuracy for women but added little for men, so the formulas diverged.

Can I use cm and get the same result as inches?

Yes — the calculator converts your metric measurements to inches internally before applying the formula, since the original coefficients were fit on inch data. You should get equivalent results either way.

Body Fat Calculator

Estimate body fat percentage from waist, neck and (for women) hip measurements using the US Navy circumference formula, in cm or inches.

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Formula: Men: 495/(1.0324 − 0.19077·log10(waist−neck) + 0.15456·log10(height)) − 450 (inches); Women adds hip and different constants

Worked examples

Man, 180 cm, waist 85 cm, neck 38 cm, 80 kg
A typical fit-range male result using only three tape-measure circumferences plus height.
Woman, 160 cm, waist 90 cm, neck 33 cm, hip 105 cm, 68 kg
The female formula adds a hip measurement because fat distribution patterns differ from men's.
Man, 70 in, waist 34 in, neck 15 in (imperial)
Same US Navy formula entered directly in inches — no weight given, so only the percentage and category are returned.

What this calculator estimates

Body fat percentage is the share of your total weight that is fat mass rather than muscle, bone, organs and water. This tool estimates it using the US Navy circumference method, a tape-measure-only approach that needs no calipers, scales or scans — just a few measurements around your neck, waist and (for women) hips, plus your height.

The formula and its source

The method comes from a 1984 US Navy study by Hodgdon and Beckett, which built a regression equation predicting body density from circumference measurements, then converts that density to a fat percentage using the standard Siri (1961) equation. Men's body fat depends on waist and neck circumference relative to height; women's formula adds hip circumference, because the original research found that fat distribution differences between the sexes made hip measurement meaningfully improve prediction accuracy for women but added little for men. All measurements are converted internally to inches before the formula is applied, since the original coefficients were derived from inch-based data — you can enter cm or inches and get an equivalent result either way.

How to measure

Neck: just below the larynx (Adam's apple), tape level.
Waist: at the navel for men; at the narrowest point of the torso for women, per the original protocol.
Hip (women only): at the widest point of the hips and glutes.

Measure snug against the skin but without compressing it, and take the average of two readings for consistency — small measurement errors get amplified by the formula's logarithms more than you'd expect.

How to use the result

The percentage comes with a category label (essential fat, athletic, fitness, average, or above average) based on common body-composition reference ranges, which differ between men and women because essential fat levels differ biologically. If you also enter your weight, the tool converts the percentage into estimated fat mass and lean mass in kilograms, which pairs naturally with the lean body mass and FFMI calculators elsewhere in this hub.

Accuracy and limits

Studies comparing the Navy method to DEXA scans (the imaging-based gold standard) typically find it within about 3–4 percentage points for most body types — good enough to track your own trend over weeks or months, not precise enough for clinical or research use. It's known to become less reliable at body-composition extremes, particularly for very lean or unusually proportioned individuals, where it can produce implausibly low or high numbers. Use it to monitor change over time with consistent measurement technique rather than to chase an exact number, and remember that body fat percentage alone doesn't capture health — this is an estimate, not medical advice.

Frequently asked questions

How accurate is the US Navy method?: Studies comparing it to DEXA scans generally find it within about 3–4 percentage points for most body types — good enough to track trends, not precise enough for clinical or research use. Consistent measurement technique matters more than which formula you use.
Where exactly do I measure?: Neck: just below the larynx. Waist: at the navel for men, at the narrowest point for women (per the original Navy protocol). Hip (women only): at the widest point of the hips/glutes. Measure snug but not compressed, and take the average of two readings.
Why does the female formula need a hip measurement but the male one doesn't?: The original 1984 Navy study (Hodgdon & Beckett) found that fat distribution differences between sexes meant hip circumference improved prediction accuracy for women but added little for men, so the formulas diverged.
Can I use cm and get the same result as inches?: Yes — the calculator converts your metric measurements to inches internally before applying the formula, since the original coefficients were fit on inch data. You should get equivalent results either way.

These calculators give general estimates from published formulas. They are not medical advice and do not account for your individual health; talk to a qualified professional before changing your diet or training.