Body Fat %

The US Navy body fat method estimates body fat percentage from a few tape-measure circumference measurements: neck, waist, height, and (for women) hip. It is one of the few easy at-home methods that does not require expensive equipment, and it is reasonably accurate compared to gold standards like DEXA scans.

Body fat percentage is a more direct measure of body composition than BMI. Two people with the same BMI can have very different body fat percentages.

Body fat ranges (adults)

Approximate ranges from the American Council on Exercise:

• Essential fat: men 2–5%, women 10–13%
• Athletes: men 6–13%, women 14–20%
• Fitness: men 14–17%, women 21–24%
• Average: men 18–24%, women 25–31%
• Obese: men ≥ 25%, women ≥ 32%

The formulas

Men:

BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76

Women:

BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387

All measurements in inches. Measure consistently: relaxed posture, tape firm but not compressing the skin.

Worked example

A man, 70 inches tall, 36-inch waist, 15-inch neck:

• waist − neck = 21
• BF% = 86.010 × log10(21) − 70.041 × log10(70) + 36.76
• BF% ≈ 86.010 × 1.3222 − 70.041 × 1.8451 + 36.76
• BF% ≈ 113.74 − 129.23 + 36.76 ≈ 21.3%

Interpretation: roughly average for an adult man.

When this is useful

Tracking changes over time at home, when a gym scale or DEXA scan is not accessible. Consistent measurement technique matters more than absolute accuracy — if you measure the same way every time, the trend is what you care about.

Caveats

The Navy method has an error margin of roughly ±3 percentage points compared to DEXA scans. It works less well for very lean or very obese individuals. For medical decisions, use a clinical method (DEXA, hydrostatic weighing, or BodPod), not a circumference calculator.

Frequently asked questions

Related tools

• BMI Calculator
• Calorie (TDEE)
• Ideal Weight