Body Fat Percentage Calculator
Free body fat calculator. Estimate body fat percentage using the U.S. Navy circumference method from neck, waist, and (for women) hip measurements.
Quick answer
U.S. Navy method: body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76 (men); women add hip into the formula. Accuracy is ±3% — good enough for tracking trends, not precise enough for medical decisions. DEXA scans are the gold standard.
Body Fat Percentage Calculator
Body fat estimate
How it works
Uses the US Navy circumference method. For men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76. For women: 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387. Measure neck below the larynx, waist at the navel, hips at the widest point.
When to use it
A quick body composition estimate when you don't have a DEXA scanner or skinfold calipers. Useful for tracking changes over time — directional accuracy is better than absolute accuracy.
Common mistakes
Sucking in the gut for the waist measurement. Measure relaxed, just after exhaling. Also: comparing this number to a DEXA scan. The Navy method is typically within 3-4% of DEXA, but individual results vary.
How the body fat calculator works
The U.S. Navy circumference method uses neck, waist, and (for women) hip measurements with height to estimate body fat percentage via a logarithmic regression. The Navy developed it as a non-invasive screening tool. Accuracy is typically within ±3% of DEXA scan results for adults — good enough for tracking changes over time but not for clinical-grade precision. The calculator implements the standard Navy formulas and shows results alongside body fat category labels (essential, athlete, fitness, average, obese).
When to use it
Tracking body composition changes over time at home without equipment. Validating that a cut is preserving muscle (track lean mass, not just total weight). Setting a realistic body fat goal (10-15% for men, 18-22% for women is healthy fitness range). Comparing to BMI — a muscular athlete with normal BMI may have higher body fat % than expected, or vice versa.
Common mistakes
- Measuring inconsistently. Use a soft measuring tape, measure at the same time of day, in the same conditions. The accuracy of the formula is worse than the accuracy of your measurement technique.
- Treating one number as definitive. Skinfold calipers, BIA scales, DEXA, and the Navy method all give different numbers for the same person. Pick one method and track its trend, not absolute values across methods.
- Chasing very low body fat. Below 8% (men) and 14% (women) is unsustainable for most adults and risks hormonal issues. Aim for healthy ranges, not contest-prep extremes.
Frequently asked questions
How accurate is the Navy body fat calculator?
Typically ±3% compared to DEXA scans. Good enough for tracking trends; not precise enough for medical decisions. Accuracy depends heavily on consistent measurement technique — use the same tape, same time of day, same conditions.
What's a healthy body fat percentage?
Men: 10-22% is the healthy range, with 14-17% being athlete-level fitness. Women: 18-30% healthy, 21-24% fitness. Both have hormonal floors below which essential function is impaired (3-5% for men, 12-14% for women).
How can I lower my body fat?
Sustained calorie deficit (300-500 below maintenance), high protein (1g/lb of goal weight), resistance training, and patience. Spot reduction doesn't work — fat loss is systemic. Expect 0.5-1% body fat loss per month with consistent effort.