Body Fat Calculator
Estimate your body fat percentage with the U.S. Navy tape-measure method. Enter your height, neck, and waist (plus hips for women) to get an instant result with a fitness category.
Scales tell you your weight, not what it's made of. The U.S. Navy body fat method estimates your body fat percentage from a few simple tape measurements — no calipers or lab visit needed. Developed by Navy researchers in the 1980s and still used for military fitness screening, it gives you a percentage plus a category from Essential to Obese.
How to measure
- Neck: just below the Adam's apple, tape snug but not tight.
- Waist: at the navel (belly button).
- Keep the tape level and exhale normally before reading.
Tape-measure estimates — calipers or DEXA scans are more accurate.
How to use this calculator
- Select your sex — the formula and required measurements differ.
- Enter your height in inches.
- Measure and enter your neck circumference in inches.
- Measure and enter your waist circumference in inches (at the navel for men, narrowest point for women).
- Women: also enter hip circumference at the widest point.
- Click Calculate to see your estimated body fat percentage and category.
The formula
Hodgdon–Beckett equations (U.S. Navy, 1984). 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, with all measurements in inches.
Worked example
A 5'10" man with a 36-inch waist and a 16-inch neck has an estimated body fat of 19.4%, which falls in the Average range for men. A 5'4" woman with a 30-inch waist, 38-inch hips, and 13-inch neck estimates at 29.2%, in the Average range for women.
Frequently Asked Questions
How do I take the measurements correctly?
Use a flexible tape measure on bare skin. Measure your neck just below the Adam's apple, keeping the tape level. Men measure the waist at navel level; women measure at the narrowest point of the abdomen. Women also measure hips at the widest point of the buttocks. Measure at the end of a normal exhale, don't suck in your stomach, and take each measurement twice to check consistency.
How accurate is the Navy method?
Studies put it within about 3–4 percentage points of lab methods like DEXA for most people — good enough to track trends and get a realistic category. It's less reliable for very lean or very muscular people, since the equations assume average body proportions. If you need a precise number for athletic or medical reasons, skinfold calipers in trained hands or a DEXA scan are more accurate.
What body fat percentage is considered healthy?
For men, the commonly cited healthy range is roughly 10–20%, and for women roughly 20–30%, with athletes sitting lower. The calculator uses ACE fitness categories: Essential, Athletes, Fitness, Average, and Obese. But 'healthy' is individual — age, activity, and overall health matter more than hitting an exact number, so use the result as a guide rather than a verdict.
Why do women need a hip measurement but men don't?
The Navy equations were built by regressing body fat against circumferences separately for men and women, and the best-fitting predictors differed. Women tend to store more fat in the hips and thighs, so the hip measurement adds real predictive power for women. For men, waist and neck alone predicted body fat well enough that hips didn't improve the equation.
My result seems off — what could cause that?
The most common cause is measurement error: a tape that's not level, measuring over clothing, or sucking in the stomach can swing the result several points. Bloating, a big meal, or dehydration also shift circumferences temporarily. Re-measure carefully on a normal morning, and remember this is an estimate — if the number surprises you, verify with a second method before drawing conclusions.