Body Fat Calculator
Estimate your body fat percentage using the US Navy tape-measurement method.
Sex
cm
cm
cm
- 1
Waist − Neck
86 − 38 = 48 - 2
Siri density denominator
1.0324 − 0.19077 × 1.6812 + 0.15456 × 2.2504 = 1.05949log₁₀ values already substituted into the US Navy regression. - 3
Body fat %
495 ÷ 1.05949 − 450 = 17.2
Formula
How this is calculated
This tool uses the US Navy circumference method, which estimates body fat from tape measurements instead of a body scan. All inputs are in centimeters: height, neck, waist, and (for women) hip. Internally the formula uses base-10 logarithms of these circumferences to approximate body density, then converts density to a fat percentage via the Siri equation built into the constants (the 495 and 450 terms).
For men the key driver is waist minus neck: the formula plugs log10(waist − neck) and log10(height) into a fixed regression and returns a percentage. For women, hip circumference is added (waist + hip − neck) because women carry relatively more fat around the hips, so the female equation uses different coefficients tuned to that distribution.
The result is a statistical estimate, not a direct measurement. It assumes a typical fat distribution, so very muscular, very lean, or pregnant bodies can read inaccurately, and waist − neck must be positive for a valid number. Expect roughly 3 to 4 percent error versus hydrostatic weighing, so it is best used to track trends over time.
Examples
| Input | Result |
|---|---|
| Man: height 180 cm, neck 40 cm, waist 90 cm | Body fat about 18.4% — acceptable/fit range |
| Man: height 178 cm, neck 38 cm, waist 85 cm | Body fat about 16.4% — fit range |
| Woman: height 165 cm, neck 34 cm, waist 75 cm, hip 100 cm | Body fat about 28.9% — acceptable range |
About this calculator
Body fat percentage is the share of your total body weight that is made up of fat tissue, with the rest being lean mass such as muscle, bone, organs and water. It is a far better indicator of fitness and health risk than weight or BMI alone, because it distinguishes a lean, muscular build from one carrying excess fat at the same scale weight.
This calculator uses the US Navy circumference method, a tape-measure formula developed by the Naval Health Research Center. For men it uses height, neck and waist measurements; for women it adds the hip measurement. The equations rely on logarithms of these circumferences and produce an estimate without any special equipment. Measure at the navel for the waist, at the widest point for the hips, and just below the larynx for the neck, keeping the tape snug but not compressing the skin.
To use the tool, select your sex and unit system, then enter your height and the relevant circumferences. The calculator returns your estimated body-fat percentage and often your fat mass and lean mass in the same units.
Interpret the result against general fitness ranges. For men, roughly 6 to 13 percent is athletic, 14 to 17 percent is fit, 18 to 24 percent is acceptable, and 25 percent or more is high. For women the bands run higher because of essential fat: about 14 to 20 percent athletic, 21 to 24 percent fit, 25 to 31 percent acceptable, and 32 percent or more high.
Keep expectations realistic. The Navy method is convenient but only an estimate, typically within about 3 to 4 percentage points of a DEXA or hydrostatic measurement, and it can be thrown off by bloating, posture or a sloppy tape measurement. Take each measurement two or three times and average them, measure at the same time of day, and use the trend over weeks rather than a single reading.
Frequently asked questions
It is reasonably good for a tape-measure method, usually landing within about 3 to 4 percentage points of lab tests like DEXA or hydrostatic weighing. Accuracy depends heavily on careful, consistent measuring, so a sloppy tape placement is the main source of error.
Measure your neck just below the larynx (Adam's apple) with the tape sloping slightly down at the front. Measure your waist horizontally at the navel for men, and at the narrowest point for women, keeping the tape level and snug without squeezing the skin.
Women typically store more fat around the hips and thighs, so the female Navy formula adds the hip circumference to capture that distribution accurately. The male formula only needs neck and waist because male fat tends to concentrate around the abdomen.
For men, around 14 to 24 percent is generally healthy, and for women about 21 to 31 percent, because women carry more essential fat. Athletes run lower, while readings of 25 percent (men) or 32 percent (women) and above suggest elevated health risk.
Yes. Dropping below about 5 to 6 percent for men or 14 to 16 percent for women cuts into essential fat needed for hormones, organ protection and temperature regulation. Very low body fat can disrupt menstrual cycles, mood and immune function, so extreme leanness is not a healthy long-term target.
Also known as
TG we-Calculate Editorial Team. (2026). Body Fat Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/body-fat-calculator
TG we-Calculate Editorial Team. "Body Fat Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/body-fat-calculator.
TG we-Calculate Editorial Team, "Body Fat Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/body-fat-calculator
@misc{wecalculate_body_fat_calculator, title = {Body Fat Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/body-fat-calculator}}, year = {2026}, note = {TG we-Calculate} }
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