Body Fat Calculator

The U.S. Navy method

This calculator uses the U.S. Navy circumference formula, which estimates body-fat percentage from a few tape-measure readings instead of calipers or a scan. Men need height, neck, and waist; women also need the hip measurement. It's free, repeatable at home, and usually within a few points of a DEXA scan.

How to measure

• Neck — just below the larynx, tape sloping slightly down to the front.
• Waist — at the navel for men; at the narrowest point for women.
• Hip — at the widest point of the buttocks (women).
• Keep the tape snug but not compressing the skin, and measure on bare skin.

FAQ

How accurate is it?

The Navy method has a typical error of about ±3–4%. It's excellent for tracking change over time — take measurements the same way each week and watch the trend rather than any single reading.

Is this body fat calculator free and private?

Yes, it is free to use, and all calculations happen in your browser. Your height, weight, and tape measurements are never uploaded or stored on a server.

Why do women need a hip measurement but men don't?

The Navy formula for women includes the hip circumference because fat distribution differs between sexes, and adding the hip term improves accuracy for women. The men's formula relies on neck and waist alone, so it asks for those only.

What body fat percentage is considered healthy?

General guidelines put a healthy range at roughly 10–20% for men and 18–28% for women, with athletes often lower. These are broad reference points, not medical thresholds, so consult a doctor for personalized targets.

Should I measure in the morning or evening?

Measure at a consistent time, ideally first thing in the morning before eating or drinking, since food, water, and bloating can shift your waist reading. Consistency matters far more than the exact time of day when you are tracking progress.

Does it work on mobile?

Yes, the tool is fully responsive, so you can enter your measurements and read your result on a phone right after taping yourself.