How accurate is the US Navy body fat method?

Studies generally find it within about 3–4 percentage points of more precise methods like DEXA scans for most body types, though it can be less accurate for very lean, very muscular or very heavy people.

Where exactly do I measure my waist?

At the navel, with the tape level and snug but not compressing the skin. Measure standing up, after a normal exhale, without pulling your stomach in.

Why does the formula need a neck measurement?

Neck circumference is used as a rough baseline for someone's frame size, so subtracting it from the waist (and hip) measurement isolates roughly how much extra size is fat rather than a naturally larger build.

Why is the formula different for women?

Women typically carry more fat around the hips, so the formula adds a hip measurement and uses different constants than the men's version, which is based on waist and neck alone.

Is this the same as BMI?

No. BMI only compares height and weight, so it can't tell fat from muscle. This method estimates fat directly from body measurements, so a muscular person and a less muscular person of the same BMI can get quite different results here.

Body Fat Percentage Calculator (US Navy Method)

The US Navy method estimates body fat from your neck, waist and (for women) hip measurements, using a formula built from log-scaled circumference differences. A 32-inch waist and 15-inch neck at 5'8" puts a man at roughly 14–15% body fat, in the athletic-to-fitness range.

Sex (measured differently by the formula)

Height

Weight

Neck

Waist (at the navel)

Hip (widest point)

Estimated body fat

30.1%

Average

Essential
Athletic
Fitness
Average
Obese

Fat mass

21 kg

Lean mass

49 kg

Estimated with the US Navy circumference method, typically within a few percent of a body scan for most builds, less accurate for very lean or very heavy people. Measure the waist at the navel and keep the tape snug but not tight.

Show the math

1
Add waist and hip, then subtract neck
80 + 100 − 34 = 146 cm
= 146 cm

Read the steps as text

Add waist and hip, then subtract neck. 80 + 100 − 34 = 146 cm
Plug into the US Navy formula. 495 ÷ (1.29579 − 0.35004×log₁₀146 + 0.221×log₁₀170) − 450 = 30.1% The women's version adds a hip measurement, since fat distribution differs from men's.
Split your weight into fat and lean mass. 70 kg × 30.1% = 21 kg fat, leaving 49 kg lean mass 30.1% puts you in the "Average" range.

How the US Navy method works

Unlike BMI, which only uses height and weight, this method takes actual body measurements: your neck, your waist at the navel, and for women, your hip at its widest point. The idea is that waist size relative to neck size (and hip, for women) tracks stomach and hip fat reasonably well, while neck size stays fairly stable regardless of body fat.

The US Navy developed and validated this formula in the 1980s as a fast, no-equipment way to estimate body composition for fitness standards, and it remains one of the more accurate methods that doesn't need calipers, a scan or being submerged in water.

Getting an accurate measurement

Use a flexible tape measure, not a metal one. Measure your neck just below the larynx (Adam's apple), sloping slightly downward at the front. Measure your waist at the navel, without pulling the tape tight or sucking in your stomach. For hips, measure at the widest point around the buttocks. Take each measurement two or three times and use the average — a few millimetres of difference can shift the result by a percentage point or two.

Body fat categories and their limits

The essential-fat range is the minimum needed for basic physical and hormonal health; athletic and fitness ranges are common among people who train regularly; average is typical for the general population; and the obese range carries higher health risk. These bands (from the American Council on Exercise) differ between men and women because women naturally carry more essential fat.

As with any tape-measure method, results are less reliable at the extremes — very lean, very muscular or very heavy bodies can throw the formula off by more than the usual few percentage points. A DEXA scan or hydrostatic weighing is more accurate if you need a precise number.

Frequently asked questions

How accurate is the US Navy body fat method?: Studies generally find it within about 3–4 percentage points of more precise methods like DEXA scans for most body types, though it can be less accurate for very lean, very muscular or very heavy people.
Where exactly do I measure my waist?: At the navel, with the tape level and snug but not compressing the skin. Measure standing up, after a normal exhale, without pulling your stomach in.
Why does the formula need a neck measurement?: Neck circumference is used as a rough baseline for someone's frame size, so subtracting it from the waist (and hip) measurement isolates roughly how much extra size is fat rather than a naturally larger build.
Why is the formula different for women?: Women typically carry more fat around the hips, so the formula adds a hip measurement and uses different constants than the men's version, which is based on waist and neck alone.
Is this the same as BMI?: No. BMI only compares height and weight, so it can't tell fat from muscle. This method estimates fat directly from body measurements, so a muscular person and a less muscular person of the same BMI can get quite different results here.