How this body fat calculator works
This tool uses the U.S. Navy circumference method. It was developed by Hodgdon and Beckett for the U.S. Navy in 1984, and a 2002 U.S. Department of Defense instruction uses the same equations. All measurements are in inches.
- Men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
- Women: 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387
You don't need to do this math. Enter your numbers and we do it for you. If you use centimeters, we convert them first. Your weight isn't part of the formula. We only use it to split your weight into fat mass and lean mass in the results.
How to measure
Use a soft tape measure. Keep it snug but not tight, and stand relaxed.
- Neck: just below the voice box, with the tape sloping slightly down to the front.
- Waist (men): at the belly button, at the end of a normal breath out.
- Waist (women): at the narrowest point, at the end of a normal breath out.
- Hips (women): at the widest point.
Take each measurement 2 or 3 times and use the average.
What your result means
We place your result in a band based on American Council on Exercise (ACE) ranges:
| Band | Women | Men |
|---|---|---|
| Very low | under 14% | under 6% |
| Below average (lean) | 14% to 24.9% | 6% to 17.9% |
| Average | 25% to 31% | 18% to 24% |
| Obesity range | 32% or more | 25% or more |
A result with a decimal, like 31.5% for a woman, still counts as average, since it's below the obesity line. ACE notes that levels in the very low band may be dangerously low.
You'll also see your fat mass and lean mass in pounds, stone, or kilograms. Lean mass is everything that isn't fat, like muscle, bone, organs, and water.
Limits of the tape method
This is an estimate, not a scan. Where you place the tape can change the result. The equations were built from groups of Navy men and women, so they may fit some bodies better than others. Use it to track changes over time, measured the same way each time.
To see what your number means in more detail, read our body fat percentage chart. You can also plug your result into our lean body mass calculator or FFMI calculator.