How accurate is the US Navy body fat formula?

The Navy circumference method usually lands within about 3 percentage points of DEXA scans for a general adult population, as long as the tape is placed correctly on the smallest neck point and widest waist point.

Why does the Navy formula need a hip measurement for women?

Female body fat distribution concentrates around the hips and thighs. Including the widest hip circumference lets the equation account for that pattern, which is why the female version adds hip into the log term.

Do I need inches for the formula?

The published coefficients assume inches, but any consistent unit works because the formula uses ratios and logarithms. A calculator simply converts your centimeters to inches for you.

US Navy Body Fat Formula Explained: 3 Steps, One Tape

Most people reach for the scale and get a number that means nothing about their actual shape. The U.S. Navy body fat formula flips that: instead of weight, it reads where fat actually collects — the neck and the waist, plus the hip for women.

It's free, requires only a tape measure, and for most people lands within a few points of a DEXA scan. Here's exactly how it works, and how to feed it correct numbers.

The two equations

The method splits by sex because fat distribution differs. Both use logarithms of your key circumferences relative to a baseline.

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

The formula treats the gap between your waist and neck as a proxy for central fat. The bigger that gap, the more fat is estimated — no extra gadgets required.

Measuring so the result is worth trusting

Spot	How to measure	Common mistake
Neck	Just below the larynx, tape level	Measuring too high or pulling tight
Waist	At belly-button height, relaxed	Sucking in or slumping
Hip (women)	Widest point around the glutes	Measuring too narrow

Take readings with a relaxed, standing posture, no tight clothing, ideally at the same time of day. Small tape placement changes shift the output, so consistency beats perfection.

Why your result is an estimate

The Navy method predicts body fat from shape, not actual tissue scans. Muscular individuals and people with fat concentrated in the trunk may see slightly inflated figures, while those with peripheral fat may see deflated ones. That's why we pair every reading with a range — trend tracking matters more than a single point.

Putting the formula to work

Use the FatPulse body fat calculator to run the math without a calculator, then compare two measurement sessions a month apart. A falling number alongside a stable weight means you're gaining muscle while losing fat — the real win report card behavior-trackers miss.