Body fat calculator: tape measure method
The US Navy circumference formula estimates body fat from a few tape measurements. It’s free, needs no scale, and is repeatable enough to track trends.
Short answer
Enter your height, waist and neck (plus hips for women). The US Navy formula estimates body fat percentage; results are usually within a few points of lab tests and are best used as a trend.
Calculated in your browser. Nothing you enter is sent anywhere.
How to measure
- Waist: at the navel for men; at the narrowest point for women, relaxed, after breathing out.
- Neck: just below the larynx, tape angled slightly down at the front.
- Hips (women): around the widest part of the buttocks.
Formula
Men: %BF = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. Women: %BF = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387 (all in inches). Categories follow the American Council on Exercise.
For tracking, measure the same way every few weeks and log your waist in ProgressLens beside your photos. Read how to measure body fat with a tape measure.
FAQ
Frequently asked questions
How accurate is the Navy body fat method?
Studies typically find it within about 3–4 percentage points of lab methods like DEXA for most people, less accurate at very low or high body fat. It’s consistent, which makes it useful for trends.
Can I estimate body fat from a photo?
Only roughly. Visual estimates and AI apps can be off by several points and change with light. A tape is more repeatable.
Is my data saved?
No. Everything is calculated in your browser.