Body Fat Percentage Calculator (US Navy Method)
Estimate your body fat percentage from height, neck, waist and (for women) hip circumference with the US Navy (Hodgdon-Beckett) method, plus fat mass and lean mass.
Things to keep in mind:
- The result is an estimate from circumferences and may differ from DEXA or hydrostatic weighing by a few percentage points. Measuring technique strongly affects the result.
- The formula was developed for adults aged 18 and over; children and adolescents are assessed with age- and sex-specific growth percentiles.
- Results are not reliable during pregnancy, with oedema or with conditions affecting the abdomen.
- The method may be systematically off for very muscular athletes and older adults.
- The result is an estimate, not a medical diagnosis or treatment advice; consult your physician or dietitian for decisions about your health.
Calculator
Result
Enter the values and press Calculate to see the result here.
About this tool
The US Navy method estimates body density from tape-measure circumferences, based on the equations Hodgdon and Beckett published at the Naval Health Research Center in 1984. Density is converted to body fat percentage with the Siri equation.
Formulas (all measurements in cm, log = base-10 logarithm)
- Men: density = 1.0324 − 0.19077·log(waist − neck) + 0.15456·log(height)
- Women: density = 1.29579 − 0.35004·log(waist + hip − neck) + 0.22100·log(height)
- Body fat (%) = 495 ÷ density − 450 (Siri)
- Fat mass = weight × body fat ÷ 100; lean mass = weight − fat mass
The method is practical and cheap; its typical error against hydrostatic weighing is a few percentage points. Repeating the measurement under the same conditions (morning, before eating, after breathing out) is best for tracking.
Example: for a man 180 cm tall weighing 80 kg with a 38 cm neck and an 85 cm waist, density ≈ 1.06199 and body fat ≈ 16.1 %. Fat mass is 12.9 kg and lean mass 67.1 kg.
Example 2 (woman): for a woman 165 cm tall weighing 62 kg with a 32 cm neck, 72 cm waist and 98 cm hips, body fat is 27.4 %, fat mass 17.0 kg and lean mass 45.0 kg.
How to read the result: Body fat is an estimate of the share of your body weight that is fat tissue; fat mass and lean mass are that share in kilograms. Lean mass includes muscle, bone, organs and water. Because the result is an estimate from circumferences, the change over time in repeated measurements under the same conditions is more meaningful than a single value, and a difference of a few millimetres in measurement can affect the result. Ask a health professional for comparison and assessment; the tool alone does not judge your health.
How to use
- Select your sex and enter your height and weight.
- Enter your neck and waist circumference in centimetres.
- Women: also enter the hip circumference.
- Press Calculate.
Notes
Body fat, fat mass and lean mass are rounded to 1 decimal place (HALF_UP); lean mass is weight minus the rounded fat mass. For men the waist must be larger than the neck; for women the hip circumference must be entered. Otherwise the formula is undefined and all results are 0. A negative body fat value is shown as 0.
Sources
References
- [1]Prediction of Percent Body Fat for U.S. Navy Men from Body Circumferences and HeightHodgdon JA, Beckett MB, Naval Health Research Center, 1984
- [2]Prediction of Percent Body Fat for U.S. Navy Women from Body Circumferences and HeightHodgdon JA, Beckett MB, Naval Health Research Center, 1984
Frequently asked questions
Measured correctly, it typically lies within a few percentage points of laboratory methods. The trend of repeated measurements under the same conditions is more meaningful than a single value.
The original method measures men at the navel and women at the narrowest point of the waist. Measure after breathing out, without pulling the stomach in.
Because fat distribution differs, the female equation uses waist + hip − neck. Without the hip circumference no result can be calculated.
It is your weight minus fat mass: the combined weight of muscle, bone, organs, water and other tissues.
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