How the Navy method works

This calculator uses the U.S. Navy circumference method, which estimates body fat percentage from a few tape measurements instead of calipers or a scan. For men it uses height, neck, and waist. For women it also uses the hip measurement. The formulas rely on logarithms, which is why the calculation is easy for a computer and awkward to do by hand. The method was developed for military fitness checks, where a quick, equipment-free estimate was more important than perfect precision.

How to measure correctly

Accurate measurements matter, because a small error in the waist figure changes the result noticeably. Use a flexible tape measure and keep it snug against the skin without squeezing. Measure your neck just below the larynx, with the tape sloping slightly downward at the front. Men should measure the waist at the navel, while women should measure at the narrowest part of the waist, and both should do it after a normal breath out. Measure the hips at their widest point. Take each measurement two or three times and use the average. For repeated checks, measure at the same time of day, such as first thing in the morning.

A worked example

Take a man who is 175 cm tall with a 38 cm neck and an 85 cm waist. The calculator estimates his body fat at about 16.9%. If his waist were 90 cm instead, with everything else unchanged, the estimate rises to about 20.7%. That shows how sensitive the result is to the waist measurement. For a woman who is 165 cm tall with a 33 cm neck, a 75 cm waist, and 98 cm hips, the estimate is about 28.4%.

What the numbers mean

Commonly cited ranges, such as those from the American Council on Exercise, put average body fat at roughly 18 to 24% for men and 25 to 31% for women. Fitness levels are lower, around 14 to 17% for men and 21 to 24% for women, and athletes are often lower still. Women naturally carry more essential fat than men, so the ranges differ by sex. Very low values are not automatically healthier, because the body needs a minimum amount of fat to function.

Accuracy and limits

The Navy method is usually within a few percentage points of clinical methods such as DEXA scans for most people, but it can be less accurate for very lean, very heavy, or very muscular individuals, and for older adults. It is best used to track your own trend over weeks and months rather than to chase one exact figure. For your overall picture, compare it with the BMI Calculator and the Ideal Weight Calculator. This tool gives general information only and is not medical advice.

If you want a second opinion, other methods exist. Skinfold calipers measure the thickness of fat at several body sites and are fairly accurate in trained hands. Bioelectrical impedance scales send a small current through the body and are convenient, but their readings change with hydration. DEXA scans are among the most precise options and are available at some clinics and fitness centres. Whichever method you use, stay consistent so your results are comparable over time.