Body Fat Calculator
Enter your sex, height, and neck, waist, and hip circumferences to estimate your body fat percentage using the US Navy circumference method, a tape-measure formula that needs no calipers or scans.
How to calculate body fat
The US Navy method estimates body fat from a handful of tape-measure circumferences rather than calipers or a scan. For men, it uses waist minus neck circumference and height. For women, it also factors in hip circumference, since fat distribution differs by sex. All measurements go into base-10 logarithms inside the formula, developed and validated by the US Navy as a fast, no-equipment field method.
Men: %BF = 495/(1.0324 - 0.19077 log10(waist-neck) + 0.15456 log10(height)) - 450. Women adds hip and uses different constants.
Worked example
A man is 70 inches tall with a 15-inch neck and a 34-inch waist.
- waist - neck = 34 - 15 = 19 in; log10(19) = 1.2788
- log10(70) = 1.8451
- Denominator = 1.0324 - 0.19077 x 1.2788 + 0.15456 x 1.8451 = 1.0737
- Body fat = 495 / 1.0737 - 450 = 11.1
Result: An estimated body fat percentage of about 11.1%.
Frequently asked questions
How accurate is the US Navy body fat method?
It is typically within 3 to 4 percentage points of a DEXA scan for most people, which is reasonably accurate for a tape-measure method with no equipment. It can be less reliable for people with unusual fat distribution or very high or low body-fat levels. Treat the result as a useful estimate, not a clinical measurement, and it is not medical advice.
Where do I measure neck, waist, and hip?
Measure your neck just below the larynx (Adam's apple), your waist at the narrowest point (or at the navel if there is no natural narrowing), and, for women, your hips at the widest point around the buttocks. Keep the tape snug but not compressing the skin, and measure standing upright and relaxed.
Why does the formula differ for men and women?
Women naturally carry more essential fat and distribute it differently (more around the hips), so the US Navy method adds a hip measurement and uses different constants for women to keep the estimate accurate across both sexes. Using the men's formula for a woman, or vice versa, will give a meaningfully wrong result.
What is a healthy body fat percentage?
For men, roughly 10 to 20% is considered a fit, healthy range, with under 10% athletic and over 25% categorized as obese. For women, the healthy range runs higher, roughly 18 to 28%, with under 18% athletic and over 32% categorized as obese. Ranges vary by source and age, so use them as a general guide.
How does this compare to the FFMI calculator?
This tool estimates your body-fat percentage from tape measurements. The FFMI calculator uses a body-fat percentage (measured however you like, including from this tool) plus your weight and height to score how much lean muscle you carry. Run this calculator first, then feed the result into the FFMI calculator for a fuller picture of your body composition.