How accurate is the Navy body fat method?

Compared against DEXA scanning, the Navy method typically lands within 3 to 4 percentage points, though individual errors can be larger. It performs better in the middle of the range than at the extremes, and it is sensitive to how consistently you take the tape measurements.

Where exactly do I measure?

Neck: just below the larynx, tape sloping slightly downward at the front. Waist: at the navel for men, at the narrowest point for women. Hips: at the widest point, for women only. Keep the tape snug but not compressing the skin, and measure after exhaling normally.

Why is my body fat different from what my smart scale says?

Smart scales use bioelectrical impedance, which sends a small current through the body and infers composition from resistance. That reading shifts with hydration, recent food, recent exercise and skin temperature, so it can move several percentage points across a single day. The tape method is more stable but no more precise in absolute terms.

What is a healthy body fat percentage?

Ranges differ by sex because women carry more essential fat — roughly 10 to 13 percent versus 2 to 5 percent for men. Commonly used fitness ranges are about 14 to 18 percent for men and 21 to 25 percent for women, but these describe fitness categories rather than clinical thresholds.

Body Fat Percentage Calculator

Body fat percentage is the share of your total weight made up of fat tissue. It answers the question BMI cannot: how much of your weight is fat rather than muscle, bone and water. This calculator uses the US Navy tape method and shows Relative Fat Mass alongside it, so you can see how far two respected estimates land from each other.

Estimate your body fat

All you need is a tape measure. Runs entirely in your browser.

How to take the measurements

Measurement error is the largest source of error in this method. Consistency matters more than precision — measure the same way each time.

Neck — just below the larynx, with the tape sloping slightly downward at the front. Do not flex or tuck your chin.
Waist — at the navel for men, at the narrowest point for women. Stand relaxed and measure after breathing out normally. Do not pull the stomach in.
Hips (women) — around the widest part of the buttocks, keeping the tape level all the way round.
Height — without shoes, heels together, standing straight against a wall.

Keep the tape snug enough not to sag but not tight enough to compress the skin. Taking each measurement twice and averaging removes most of the wobble.

Body fat reference ranges

Women's ranges sit higher because essential fat — the minimum needed for normal physiological function — is roughly 10–13% in women versus 2–5% in men. That difference is biological, not a matter of fitness.

Body fat percentage categories by sex
Category	Women	Men
Essential fat	0–14%	0–6%
Athletic	14–21%	6–14%
Fitness	21–25%	14–18%
Average	25–32%	18–25%
Above average	32% and above	25% and above

Why two estimates, and why they differ

This tool reports both the Navy method and Relative Fat Mass because presenting a single figure would imply a precision that tape-based estimation does not have. The Navy method uses three or four girths and a logarithmic equation developed for military fitness screening. RFM is newer and far simpler — height and waist only — and was validated against DEXA using national survey data.

When the two disagree by more than a few points, that gap is information. It usually means your measurements sit unusually relative to each other — a thick neck, or a waist that is not typical for your height — and it is a signal to treat any single number cautiously rather than to trust whichever one you prefer.

For a genuinely accurate measurement, DEXA and hydrostatic weighing remain the references. Both cost money and require a facility visit; neither is necessary for tracking a trend.

Common questions

How accurate is the Navy body fat method?: Compared against DEXA scanning, the Navy method typically lands within 3 to 4 percentage points, though individual errors can be larger. It performs better in the middle of the range than at the extremes, and it is sensitive to how consistently you take the tape measurements.
Where exactly do I measure?: Neck: just below the larynx, tape sloping slightly downward at the front. Waist: at the navel for men, at the narrowest point for women. Hips: at the widest point, for women only. Keep the tape snug but not compressing the skin, and measure after exhaling normally.
Why is my body fat different from what my smart scale says?: Smart scales use bioelectrical impedance, which sends a small current through the body and infers composition from resistance. That reading shifts with hydration, recent food, recent exercise and skin temperature, so it can move several percentage points across a single day. The tape method is more stable but no more precise in absolute terms.
What is a healthy body fat percentage?: Ranges differ by sex because women carry more essential fat — roughly 10 to 13 percent versus 2 to 5 percent for men. Commonly used fitness ranges are about 14 to 18 percent for men and 21 to 25 percent for women, but these describe fitness categories rather than clinical thresholds.