TOOLEstimate your body fat with a tape measure
This calculator uses the US Navy circumference method — the same approach the military uses for a quick body-composition check. It reads your body fat from the size of your neck and waist (and hips for women) relative to your height, so all you need is a soft tape measure. Enter your weight too and it also splits your body into fat mass and lean mass.
Body fat percentage categories
Women: 10–13% essential · 14–20% athlete · 21–24% fitness · 25–31% average · 32%+ obese
Track the trend rather than chasing an exact number. Pair this with the BMI calculator and TDEE calculator to plan a fat-loss or muscle-gain phase.
This is a general estimate for educational purposes only and is not medical advice or a diagnosis. Circumference formulas are approximations. Consult a qualified healthcare professional before making changes to diet or exercise.
How to get an accurate measurement
- Use a flexible cloth or vinyl tape, not a rigid metal one, and measure against bare skin.
- Keep the tape level and snug — firm enough to sit against the skin without compressing it.
- Neck: just below the larynx, sloping slightly down at the front. Waist: at the navel for men, at the narrowest point for women. Hips (women): around the widest part.
- Don't hold your breath or suck in — breathe normally and measure at the end of a relaxed exhale.
- Measure twice and average, and always measure at the same time of day when tracking over weeks.
Body fat vs BMI — and why the trend matters most
Where BMI only knows your height and weight, body fat percentage estimates what that weight is actually made of. That's why the two can disagree: a muscular person often reads "overweight" on BMI while sitting at an athletic body fat level. Reading them together gives a far truer picture than either alone.
No tape-measure formula is exact, so the single most useful thing you can do is measure consistently and watch the direction of travel. A number that drifts down over a month means your plan is working, regardless of the exact starting figure. Pair this with the ideal weight calculator for a target and the TDEE calculator to set the calories that move the number.
Frequently asked questions
How does the US Navy body fat method work?
It estimates body fat from the circumference of your neck and waist (plus hips for women) relative to your height. These measurements correlate with body fat, so the formula returns a percentage without needing calipers or a scan.
How accurate is this body fat calculator?
The Navy method is typically within about 3 to 4 percent of a DEXA scan for most people, which is good for a free tape-measure estimate. Accuracy depends on measuring carefully at the right spots. Use it to track trends over time rather than as an exact figure.
Where do I measure my waist and neck?
Measure your neck just below the larynx, your waist at the navel for men and at the narrowest point for women, and hips at the widest point for women. Keep the tape snug and level, and measure without holding your breath.