Body Fat Calculator
Estimate body fat percentage using the US Navy tape measurement method.
Please note: For general information only. This is not medical advice — speak to a doctor or registered dietitian before changing your diet, training or medication.
What the Body Fat Calculator does
The US Navy circumference method estimates body fat from tape measurements of the neck, waist and (for women) hips, scaled by height. It is far more informative than BMI because it separates fat from lean mass.
Formula
Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450Women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)) − 450
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Sex | one of 2 options | Yes | — |
| Units | one of 2 options | Yes | — |
| Height | cm or in | Yes | Accepts 1 or more. |
| Neck circumference | cm or in | Yes | Accepts 1 or more. |
| Waist circumference | cm or in | Yes | At the navel for men, at the narrowest point for women. Accepts 1 or more. |
| Hip circumference | cm or in | Yes | Accepts 1 or more. |
| Weight | kg or lb | Optional | Accepts 1 or more. |
How to use it
- Choose Sex and Units.
- Enter Height, Neck circumference, Waist circumference and Hip circumference.
- Optionally add Weight.
- Select Calculate.
Worked example
A man 180 cm tall, 38 cm neck, 85 cm waist.
- Sex
- Male
- Height
- 180
- Neck
- 38
- Waist
- 85
About 17.4% body fat — the fitness range.
Frequently asked questions
How accurate is the tape method?
Within about 3–4 percentage points of a DEXA scan for most people. Its real strength is consistency — it tracks change over time reliably even if the absolute number is slightly off.
What body fat percentage should I aim for?
For general health, roughly 10–20% for men and 18–28% for women. Going near the essential-fat floor is not sustainable or healthy long term.
Method and sources
Method. The US Navy circumference method: body fat is estimated from tape measurements of neck and waist (plus hips for women) scaled against height, using the published logarithmic regression.
Assumptions
- Measurements are taken with a flexible tape held snug but not compressing the skin, at the same point and time of day each time.
- The regression was derived from adult populations and assumes a broadly typical fat distribution for the sex recorded.
Limitations
- An estimate from proportions, not a measurement of tissue. Published comparisons against hydrostatic weighing and DEXA show typical errors of several percentage points for an individual.
- It reads high for people carrying weight centrally with little fat, and low for those with thin waists and higher limb fat, because the only thing it can see is circumference.
- Not validated for children, pregnancy, or people whose body shape sits far outside the population it was derived from.
Sources
- Body composition assessment from circumference measurements (US Navy method) — Naval Health Research Center. The regression coefficients used for both the male and female formulas.