How the body fat calculator works
The U.S. Navy method estimates body fat from a few tape-measure circumferences, using a logarithmic formula validated against more precise (but less accessible) methods like hydrostatic weighing:
Men: BF% = 495 / (1.0324 − 0.19077×log10(waist−neck) + 0.15456×log10(height)) − 450
Women: BF% = 495 / (1.29579 − 0.35004×log10(waist+hip−neck) + 0.22100×log10(height)) − 450
Women: BF% = 495 / (1.29579 − 0.35004×log10(waist+hip−neck) + 0.22100×log10(height)) − 450
All measurements in centimetres.
Step-by-step guide
- Select your biological sex.
- Measure your neck circumference just below the larynx.
- Measure your waist at the navel (men) or narrowest point (women); women also measure hips at the widest point.
- Enter your height and read the estimated body fat percentage and category.
Measuring accurately
Use a flexible tape measure, keep it snug but not compressing the skin, and measure at the end of a normal exhale for consistency. Small measurement errors can shift the result by a few percentage points, so re-measure if a result looks off from what you'd expect.
Frequently asked questions
It's reasonably accurate for most body types (typically within a few percentage points of DEXA scan results in validation studies) but can be less reliable for very lean or very high body-fat individuals, and measurement technique significantly affects accuracy.
Commonly cited healthy ranges are roughly 8–20% for men and 21–33% for women, though 'healthy' varies with age, athletic goals, and individual context — treat these as general reference bands, not strict targets.
Body fat distribution patterns differ by sex on average, so the Navy method includes a hip measurement for women to account for typically higher hip-area fat storage.