Body Fat Calculator: US Navy Method from Tape Measures

How to use it

Choose Metric or Imperial and select your Sex.
Enter your Height, Neck and Waist. Women also enter the Hip (women only).
Add your Weight (optional) to see the fat mass and lean mass.
Read the Body fat figure and its Category in the result.

How the US Navy method calculates body fat

The method estimates body fat from circumferences and height, with no equipment beyond a tape measure. The equations were published by Hodgdon and Beckett in 1984 for the US Navy: report 84-11 covers men and report 84-29 covers women. The metric equations use centimetres; the inch equations use the same measurements in inches.

The result is an estimate. It can differ from a laboratory test, and it is not medical advice: talk to a doctor about your body composition and your health before you change your diet or training.

Men, cm:        495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450
Women, cm:      495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.22100 x log10(height)) - 450
Men, inches:    86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76
Women, inches:  163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387

The categories

The category uses the ranges of the American Council on Exercise (ACE). The ranges differ for men and women, because women carry more essential fat. ACE gives the average range for a man who is not an athlete as 18% to 24% and for a woman as 25% to 31%.

Category	Men	Women
Essential fat	2% to 5%	10% to 13%
Athletes	6% to 13%	14% to 20%
Fitness	14% to 17%	21% to 24%
Average	18% to 24%	25% to 31%
Obese	25% and over	32% and over

What a tape measure cannot tell you

The method is an estimate, and its error is larger than that of a DXA scan or underwater weighing.
It does not show where fat is stored or whether you have muscle or water changes.
The category describes body fat only. It is not a diagnosis.

Worked example: woman, 165 cm, neck 33 cm, waist 75 cm, hip 98 cm, 60 kg

The waist plus hip minus neck is 75 + 98 - 33 = 140 cm. The density term is 1.29579 - 0.35004 x log10(140) + 0.22100 x log10(165) = 1.29579 - 0.75124 + 0.49007 = 1.03462.

So the body fat is 495 / 1.03462 - 450 = 28.4%. That is in the average range for a woman. Her fat mass is 60 x 28.4% = 17.1 kg and her lean mass is 42.9 kg.

	Result
Body fat	28.4%
Category	Average
Fat mass	17.1 kg
Lean mass	42.9 kg

Frequently asked questions

How accurate is the US Navy method?

It is an estimate from tape measurements. It can differ from more precise tests such as a DXA scan or underwater weighing, so use it to follow your own trend, measured the same way each time.

Why does the women's formula need the hip measurement?

The women's equation includes the hip, and the men's equation does not. Enter the hip only if you are a woman; for a man it is ignored.

Why is my result different from my bathroom scale?

Scales estimate body fat from electrical resistance, which changes with hydration, while the tape method estimates it from body size. The two use different information, so they will not match exactly.

What does the category tell me about my health?

The category only places your body fat in the American Council on Exercise ranges. It is not a diagnosis; a doctor can explain what your result means for your health.

Why must the waist be larger than the neck?

The formula takes the logarithm of the waist minus the neck, which is only defined when the difference is positive. A difference that is too small gives a result that does not fit the formula, so the calculator asks you to measure again.

Does the calculator store my measurements?

No. The result is calculated in your browser and nothing you enter is sent to us.

Sources

Figures and text last checked on Tuesday, November 10, 2026.

Result