Body Fat Calculator (US Navy Method)
Measure your neck, waist and (for women) hips with a tape, then enter them with your height to estimate body fat percentage.
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Formula
US Navy method, with all measurements in centimetres (inches are converted at 2.54):
- Men:
body fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450 - Women:
body fat % = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
Categories follow the American Council on Exercise: for men essential below 6, athletes 6 to 13, fitness 14 to 17, average 18 to 24, obese 25 and over; for women essential below 14, athletes 14 to 20, fitness 21 to 24, average 25 to 31, obese 32 and over.
Worked example
A man 180 cm tall, neck 38 cm, waist 90 cm: waist − neck = 52, log10(52) = 1.716, log10(180) = 2.255. Density term: 1.0324 − 0.19077 × 1.716 + 0.15456 × 2.255 = 1.0535, so 495 ÷ 1.0535 − 450 = 19.8 %, in the average range.
Frequently asked questions
How does the US Navy body fat method work?
It estimates body density from circumference measurements and height, then converts density to a percentage. For a man 180 cm tall with a 38 cm neck and 90 cm waist, the result is about 19.8 percent.
How do I measure myself correctly?
Use a flexible tape, keep it level and snug without squeezing. Measure the neck just below the larynx, the waist at the navel for men and at the narrowest point for women, and the hips at their widest point. Take each twice and average.
What is a healthy body fat percentage?
Common American Council on Exercise ranges: men are athletic at 6 to 13 percent, fit at 14 to 17 and average at 18 to 24. Women are athletic at 14 to 20, fit at 21 to 24 and average at 25 to 31. Ranges differ between sources.
How accurate is this estimate?
It is an estimate, typically within a few percentage points of other methods, and less reliable for very lean, very muscular or very heavy bodies. Scans such as DEXA are more precise. It is not medical advice.