Body Fat Calculator

Why body fat beats weight

Your weight cannot tell fat from muscle, water or bone. Two people at 180 lb can be at 15% and 35% body fat, with very different health outlooks.

Tracking body fat is especially useful while losing weight. If the scale drops but your body fat percentage barely moves, you are probably losing muscle, which slows your metabolism and makes regain more likely.

How the US Navy method works

The Navy equations estimate body fat from your height, neck and waist, plus hips for women. They were built to assess service members quickly and have been checked against lab methods many times.

For most adults the estimate lands within about three to four percentage points of a DEXA scan. That is less precise than a scan, but good enough to track the direction of change month to month, as long as you measure the same way each time.

Healthy body fat ranges

Men need at least 2 to 5% body fat for normal function, and women 10 to 13%. For general health, most men sit comfortably between 14 and 24%, and most women between 21 and 31%.

Above 25% for men and 32% for women, the risk of type 2 diabetes, fatty liver and heart disease rises. Very low body fat carries its own risks, including hormone disruption, particularly for women.

Getting a consistent reading

Measure in the morning before eating, with the tape level and snug but not tight. Take each measurement twice and use the average. Changes of a percent or two between readings are normal noise; look at the trend across several weeks.