Body fat calculator

The U.S. Navy method estimates body fat from circumference measurements rather than skinfold calipers or a scan. For men, it uses neck and waist circumference and height in a logarithmic formula: %BF = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76, with all measurements in inches.

It is typically within about 3-4 percentage points of a DEXA scan for most men — good enough to track progress, not precise enough to treat as an exact number. Its real strength is consistency: measure the same way every few weeks and the trend is reliable, even if the absolute figure is an estimate.

Common reference ranges for men: essential fat is roughly 2-5%, athletic is about 6-13%, fitness is about 14-17%, average is about 18-24%, and 25% or higher is above average. Visible abs typically start to appear in the low-to-mid teens. For men 25-40, the average band is the most common starting point.

Measure relaxed, not flexed or sucked in. Take the waist at the level of the navel, and the neck just below the larynx with the tape sloping slightly down to the front. Keep the tape snug against the skin without compressing it, and measure at the same time of day each time for consistent tracking.

This calculator was built and is maintained by Kris Oddo, a NASM-certified personal trainer (NASM-CPT), and uses the U.S. Navy circumference method — a tape-measure approach NASM-certified coaches commonly use in practice because it needs no calipers or scan. NASM itself is a certification body, not a single formula: NASM-CPTs assess body fat with circumference methods like this one, skinfold calipers, or bioelectrical impedance depending on the setting.

Run a sustained, modest calorie deficit while resistance training and keeping protein high — that loses fat while protecting lean mass, so your body fat percentage drops without you just getting smaller. That is body recomposition. Crash diets lower bodyweight but often raise body fat percentage by burning muscle.