How to Calculate Percent Body Fat from Height, Waist, and Neck Measurements (for Men)

The US Navy Body Density Approximation Method

There are several ways to estimate percent body fat based on measurements of the human body. One method, developed by the US Navy, uses a man's height and his measurements at the neck and waist. This method of actually yields two body metrics: body density and percent body fat. You can apply the formulas below with a hand calculator, or use the convenient body fat calculator on the left.

To use the formula, first measure your height in inches and call this number H. Next, use a tape measure to find the circumference of your waist in inches, and call this number W. Lastly, measure your approximate neck girth in inches. For the neck measurement, measure around the base of your neck and allow the tape measure to gently slope downward like a "V" in the front. Call this number N.


Now, use the following formula to approximate your body density, BD:


BD = 1.01774 - 0.19077(log(W-N)) + 0.15456(log(H))

Here the log function is logarithm base 10. Once you have calculated the body's density, you can use that number to approximate the percent body fat. The formula is

%BF = 495/BD - 450

Example: Suppose a man is 68 inches tall, his waist is 33 inches, and his neck girth is 18 inches. Then we have H = 68, W = 33, and N = 18. Using the body density formula, we compute

BD = 1.01774 - 0.19077(log(33-18)) + 0.15456(log(68))
= 1.07661

To find his percent body fat, we compute

%BF = 495/1.07661 - 450
= 459.78 - 450
= 9.78

So this man's body fat is about 9.78%. Note that this is only a rough estimate based on few data points. There are more accurate ways of measuring percent body fat, such as DXA (dual energy X-ray absorptiometry) or near-infrared interactance.


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