Overview
What this calculator does
Estimate your body fat percentage using the US Navy circumference method — a free, tape-measure approach used by the military. Enter your height, neck, and waist (plus hip for women) and get your body fat percentage, category, and optional fat mass and lean mass. It works in metric or imperial.
Accuracy starts here
How to measure correctly
The result is only as good as your measurements. Use a flexible cloth or vinyl tape, pulled snug but not compressing the skin:
- Neck: just below the larynx (Adam's apple), tape sloping slightly down to the front
- Waist: at the navel for men; at the narrowest point for women
- Hip (women): around the widest part of the hips and buttocks
- Height: standing straight, without shoes
- Measure on bare skin, breathing normally, and take each measurement twice
What the number means
Body fat categories
| Men | Women | |
|---|---|---|
| Essential fat | 2-5% | 10-13% |
| Athletes | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Above average | 25%+ | 32%+ |
Women naturally carry more essential fat than men for hormonal and reproductive health, which is why the healthy ranges are higher.
Set expectations
How accurate is the Navy method?
A good estimate, not a lab result
Why composition matters
Body fat vs BMI
BMI compares your weight to your height but can't tell muscle from fat — a muscular athlete can register as "overweight" on BMI while having low body fat. Body fat percentage measures composition directly, so it's more informative for fitness goals. Use body fat for body composition and BMI as a quick screening number.
Behind the scenes
Privacy and how it runs
Your measurements stay private
Common questions
What is a healthy body fat percentage?
For men, roughly 10-20% (fitness to average); for women, 18-28%. Athletes are often lower. Going too low (below essential fat) is unhealthy. The ideal depends on your goals and overall health.
How do I lower my body fat percentage?
A modest calorie deficit, enough protein to preserve muscle, resistance training, and general activity. Lowering body fat is a gradual process — aim for steady changes over months, not weeks.
Why does the female formula need a hip measurement?
Body fat distributes differently between sexes, so the female version of the Navy formula adds the hip circumference to account for it. The male formula uses neck and waist relative to height.
What is lean body mass?
Everything in your body that isn't fat — muscle, bone, organs, and water. If you enter your weight, the calculator splits it into fat mass and lean mass based on the estimated percentage.
Is the Navy method better than calipers?
They're comparable in accuracy for most people. The Navy method needs only a tape measure and is more repeatable since it doesn't depend on pinching skinfolds consistently. DEXA scans remain the gold standard if you want maximum precision.
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Last reviewed: · Methodology based on US building code standards, contractor pricing surveys, and manufacturer specifications.