Body Fat Calculator
US Navy Body Fat Calculator
Get your body fat percentage with just a tape measure. The US Navy method (Hodgdon-Beckett 1984) is accurate within ±3-4% of DEXA scans. No calipers, no scales, no special equipment.
Last updated: April 30, 2026
Just below the larynx (Adam's apple), tape level.
Men: at the navel. Women: at the narrowest point.
Widest point of the buttocks/hips.
Your body fat
Enter your measurements
Body fat mass
— lb
⚠️ The Navy method is less accurate at this body fat range. Consider DEXA or calipers for better precision.
Body fat percentage ranges
American Council on Exercise (ACE) reference ranges for adults.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2-5% | 10-13% |
| Athletes | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Obese | 25%+ | 32%+ |
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How this calculator works
The US Navy body fat formula was developed by Hodgdon and Beckett at the Naval Health Research Center in 1984. It uses circumference measurements that correlate with body density, then converts density to body fat percentage.
Formulas (measurements in inches)
Male: % Body Fat = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Female: % Body Fat = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
How to measure correctly
- Neck: Just below the larynx (Adam's apple). Keep tape level, no slope. Don't flare your neck.
- Waist (men): At the level of your navel. Stand relaxed. Don't suck in your stomach.
- Waist (women): At the narrowest point of your torso (typically midway between lowest rib and top of hip bone).
- Hip (women only): At the widest point of your buttocks.
- Use a flexible tape measure. Take each measurement 2-3 times, use the average.
Accuracy and limitations
±3-4% accurate vs DEXA scans for most adults with 15-30% body fat. Less accurate at extremes: lean athletes under 10% (men) or 18% (women) tend to be overestimated; severe obesity tends to be underestimated. The formula cannot distinguish muscle from fat at the waist, so heavily muscled individuals may get inflated readings.
Source
Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, San Diego, 1984. Technical Report 84-11 and 84-29.
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Frequently asked questions
How accurate is the US Navy body fat calculator?
The US Navy method is accurate within ±3-4% of DEXA scans for most adults with 15-30% body fat. Lean athletes under 10% body fat (men) or 18% (women) often see overestimates, and severe obesity tends to be underestimated. For tracking trends over time with consistent measurement technique, it's reliable enough for most fitness goals.
How do I measure my waist for the body fat calculator?
For men, measure horizontally at the level of your navel without sucking in your stomach. For women, measure at the narrowest point of your torso, typically between your lowest rib and the top of your hip bone. Take the measurement on bare skin with a flexible tape, level all the way around, and take 2-3 readings to average them. A self-retracting tape measure with millimeter markings makes a real difference: a regular sewing tape stretches and rounds inconsistently. See Myotape on Amazon.
Why is body fat percentage better than BMI?
BMI uses only height and weight, so it can't tell muscle from fat. A bodybuilder and a sedentary person of the same height and weight get the same BMI despite very different body compositions. Body fat percentage measures composition directly, making it a better health and fitness indicator for most people.
What is a healthy body fat percentage by age?
For men, the American Council on Exercise considers 14-24% healthy depending on fitness level. For women, the healthy range is 21-31%. These ranges shift slightly with age: people over 40 typically carry 2-5% more body fat than younger adults at the same fitness level, and this is normal.
Can I use this calculator if I'm very muscular?
The Navy method tends to overestimate body fat for very muscular people because it can't distinguish a thick waist from muscle versus a thick waist from fat. If your waist circumference is unusually large for your visible leanness, expect this calculator to read 2-5% higher than reality. DEXA scans or skinfold calipers are more accurate for muscular individuals.
How often should I measure my body fat percentage?
Once every 2-4 weeks is enough for most people. Daily fluctuations from water retention, food, and digestion make day-to-day comparisons meaningless. For trend tracking, take measurements at the same time of day, in the same conditions (typically morning, fasted), and compare the rolling average over weeks.
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