How to measure body fat at home with tape

The US Navy circumference method needs nothing but a tape measure and a phone. It is not clinical — a DEXA scan would be — but it is consistent enough to track direction of travel over weeks, which is what most people actually need.

What you need

• A soft tape measure (cloth or fiberglass, not metal)
• A mirror, so you can see the back of your waist
• The body fat calculator on this site

Where to measure

Neck

Measure just under the larynx (Adam's apple), with the tape sloping downward slightly to the front. Keep the shoulders relaxed. Do not puff your neck or suck in your cheeks.

Waist

Measure at the navel (umbilicus), at the same point regardless of whether you're inhaling or exhaling. Keep the tape level and snug but not tight against the skin. Use a mirror to ensure it is square to your torso.

Hips (women only)

Measure at the widest part of your hips and buttocks, typically around the greater trochanters. Stand straight, feet together, weight evenly distributed.

Measuring tips

• Measure at the same time of day, ideally in the morning after using the bathroom.
• Measure consistently — same clothing, same posture, same level of breath.
• The tape should be snug but not compressing skin.
• Do not round up or pull tighter to "get a better number."

Tracking over time

A single measurement is an estimate with single-digit-percentage-point uncertainty. What it is good for is the trend: measure every two weeks, record the number, and watch the direction. If your waist is shrinking faster than your neck, your body-fat percentage is falling, regardless of the exact number.

For the lean body mass calculator and FFMI calculator, you need a body-fat figure. This method is how you get one without a scale or a clinic.

When this method is unreliable

The equation was derived on a specific population (U.S. military personnel, 1964). It degrades outside it — at very high or very low body-fat percentages, in older adults, and in people whose body composition differs from the sample. For precision, use DEXA, BIA, or skinfolds with a trained tester.

Formulas are estimates, not medical advice.

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