How to Calculate Body Fat Percentage — US Navy Method

Body fat percentage is a far more meaningful health metric than weight or BMI alone, because it directly measures the proportion of your body that is fat versus lean mass (muscle, bone, organs, water). Two people with identical weight and height can have very different body fat percentages, and very different health implications. This guide explains the most widely used at-home method: the US Navy circumference formula.

The US Navy Body Fat Formula

This method uses only a tape measure — no calipers or scales needed. For men: Body Fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76 (all measurements in inches). For women: Body Fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387.

How to Take the Measurements Correctly

• •Neck: measure just below the larynx (Adam's apple), with the tape sloping slightly downward to the front.
• •Waist (men): measure at the navel, standing relaxed (not flexed or sucked in).
• •Waist (women): measure at the narrowest point, usually just above the navel.
• •Hip (women only): measure at the widest point around the buttocks.
• •Height: measure barefoot, standing straight against a wall.

Worked Example — Male

A man: height 70 inches, neck 15 inches, waist 34 inches. Waist − neck = 19. Body Fat % = 86.010 × log₁₀(19) − 70.041 × log₁₀(70) + 36.76 = 86.010 × 1.2788 − 70.041 × 1.8451 + 36.76 ≈ 110.0 − 129.2 + 36.76 ≈ 17.6%.

Healthy Body Fat Percentage Ranges

• •Men — Athletic: 6–13%, Fitness: 14–17%, Average: 18–24%, Above Average: 25%+
• •Women — Athletic: 14–20%, Fitness: 21–24%, Average: 25–31%, Above Average: 32%+
• •Essential fat (the bare minimum needed for health): roughly 2–5% for men, 10–13% for women.

Is This Formula Accurate?

The US Navy formula is reasonably accurate for most people — typically within 3–4% of more precise lab methods like DEXA scans or hydrostatic weighing — making it a solid free, at-home estimate. It tends to be less accurate for people at the extremes of height or body composition (very tall, very short, or very muscular individuals), where it can over- or under-estimate body fat slightly. If you need an official military-standard measurement, the US Army uses a related but distinct tape test with its own standards by age and gender.