A DEXA scan is the gold standard for measuring body fat percentage, but it's expensive and not something most people have easy access to. The U.S. Navy circumference method offers a surprisingly reliable estimate using nothing more than a tape measure and a few simple body measurements.
The method uses waist, neck, and (for women) hip circumference, combined with height, in a logarithmic formula developed and validated for the U.S. Navy's fitness assessments. It's not as precise as a lab measurement, but studies have found it typically lands within about 3-4% of DEXA scan results for most people — accurate enough to meaningfully track trends over time, even if not exact to the decimal.
How Body Fat Is Estimated
For men: Body Fat % = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
For women: Body Fat % = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
Measure your neck just below the larynx, waist at its narrowest point (men) or belly button level (women), and hip at its widest point (women), all with the tape snug but not compressing the skin.
A Worked Example
For a man with a 34-inch waist, 15-inch neck, and 68-inch height: plugging into the formula produces an estimated body fat percentage in the mid-to-high teens — a reasonable, athletic-to-average range. Small measurement errors (even half an inch on the waist) can shift the result by a percentage point or two, which is why consistent measuring technique matters more than measuring once and treating the number as exact.
Common Mistakes to Avoid
- Measuring inconsistently between checks: use the same time of day, same tape tension, and same landmarks every time for the trend to be meaningful.
- Expecting lab-level precision: treat the result as a useful estimate for tracking change over time, not a medical-grade diagnosis.
- Measuring over clothing: this adds inconsistent bulk to the measurement — measure directly against skin for accuracy.
- Comparing your number directly to someone else's without context: healthy body fat ranges differ by age and sex — compare your own trend over time rather than to another person's single number.
Bottom Line
You don't need expensive equipment to get a genuinely useful body fat estimate. Use a Body Fat Calculator with your waist, neck, and height measurements to get your estimate, and re-measure periodically to track real change over time.