Body fat calculator

All you need is a tape measure. Uses the U.S. Navy circumference method.

Units
Height ft and in

Weight is optional. Add it to see your lean and fat mass.

How to measure

  1. Waist: stand relaxed, tape level around your belly button. Don't suck in.
  2. Hips: tape around the widest part of your hips and glutes.
  3. Neck: just below where it meets your shoulders, tape sloping slightly down toward the front.
  4. Measure each twice and use the average. Same time of day each time you check.

A flexible body tape measure with a locking end makes measuring yourself much easier than a sewing tape.

How accurate is it?

The Navy formula estimates body fat from the relationship between waist, hips, neck and height. For most women it lands within a few percentage points of lab methods. Its real value is tracking: if your number trends down while your weight holds steady, you're losing fat and keeping muscle. Expect normal week-to-week swings from water retention around your cycle — track the trend, not any single number.