Body Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy circumference method — just a few tape-measure measurements, no calipers or scans required.
Units
Sex
Estimated body fat
17.5%
How it's calculated
The U.S. Navy method estimates body fat from circumference measurements: neck, waist, and height for men; neck, waist, hip, and height for women. It uses logarithms of these measurements rather than simple ratios, which fits body fat data better than a linear formula.
For men: body fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. For women: body fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387 (all measurements in inches internally; this calculator converts automatically if you enter metric units).
Measure your neck just below the larynx, your waist at the navel, and (for women) your hips at the widest point, keeping the tape snug but not compressing the skin, for the most accurate result.
Worked example
A man who is 5'10" tall with a 38 cm neck and 86 cm waist has an estimated body fat of about 17.3%.
A woman who is 5'5" tall with a 32 cm neck, 71 cm waist, and 96 cm hip measurement has an estimated body fat of about 26.1%.
Frequently Asked Questions
- How accurate is the Navy method?
- It's generally accurate within a few percentage points for most body types when measurements are taken carefully, making it a convenient at-home alternative to calipers or DEXA scans — but it's still an estimate, not a clinical measurement.
- Why does the formula need my hip measurement if I'm a woman but not if I'm a man?
- The Navy method uses different formulas for men and women because fat distribution patterns differ by sex on average — the women's formula was found to be more accurate when it included hip circumference, while the men's formula performs well with just neck and waist.
- Where exactly should I measure my waist?
- Measure at your navel (belly button) level, not necessarily the narrowest point of your torso — this is the standard reference point used in the Navy method's original validation.