Body fat calculator

How does the Navy body fat formula work?

It estimates body fat from height and a few tape measurements. For men: 86.010 × log₁₀(abdomen − neck) − 70.041 × log₁₀(height) + 36.76, all in inches. A man 70 inches tall with a 15-inch neck and a 34-inch abdomen comes out at 17.5%.

And for women?

163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. A woman 64 inches tall with a 13-inch neck, 28-inch waist and 38-inch hips comes out at 26.6%.

Where do I measure?

In the DoD procedure, men measure the abdomen at the navel; women measure the waist at its narrowest point and the hips. The neck is measured too; keep the tape level and snug.

How accurate is it?

It is an estimate from measurements, not a lab test — body fat scans and other methods can give different numbers. It is best for tracking your own change over time with the same measurements.

Is this the formula the military uses today?

It is the formula from DoD Instruction 1308.3 (2002). That instruction has since been replaced, and the services now also use other screening measures.

How much does a measuring error change the result?

A lot. For a man 72 inches tall with a 16-inch neck, an abdomen of 36 inches gives 18.6% and one of 37 inches gives 20.4%. A one-inch difference in how tightly the tape is held can move the estimate by about 1.8 percentage points.

Why do men and women measure different places?

The Navy equations are separate for each sex and use different sites, as listed above: the abdomen and neck for men, and the waist, hips and neck for women. Pick the sex first, then enter the measurements the form asks for.

Can I compare my result with someone else's?

Only roughly. Differences between people in where they carry fat, muscle mass and how the tape was held all change the estimate. The result is most useful when you measure yourself the same way each time.

How the calculation works

The Navy method uses circumferences instead of weight. For men it uses the abdomen minus the neck, and for women the waist plus the hips minus the neck. The logarithm (base 10) of that number and of the height, all in inches, goes into the formula quoted above. If you enter centimeters, the calculator converts them to inches first. The formula gives a percentage of body weight that is fat. It was developed to screen military personnel with a tape measure, and it estimates fat; it does not measure it.

Worked example

A man is 72 inches tall, with a 16-inch neck and an abdomen of 36 inches at the navel. The abdomen minus the neck is 20 inches. The formula 86.010 × log₁₀(20) − 70.041 × log₁₀(72) + 36.76 gives 18.6%. For a woman 66 inches tall with a 13.5-inch neck, a 30-inch waist and 40-inch hips, waist plus hip minus neck is 56.5 inches, and the result is 29.8%. If she measured her hips one inch larger, the estimate would be 31.1%.

Common mistakes

• Measuring in the wrong place. Men measure the abdomen at the navel and women measure the waist at its narrowest point. Using the belt line for one and the narrowest point for the other gives a different number.
• Pulling the tape too tight or letting it sag. The tape should be level and snug but not compressing the skin. Take each measurement more than once and use the average.
• Treating the number as a medical result. It is an estimate from measurements. Use it to follow your own trend and compare it with other methods only roughly.

Sources and related calculators

Formula: the U.S. Department of Defense circumference method, as set out in DoD Instruction 1308.3 (2002), with the Navy equations quoted on this page. Related: Army body fat calculator, waist-to-hip ratio calculator and lean body mass calculator.

For general information only — not medical advice. Talk with your doctor or another health professional about your own health. How we check our calculators.