Body Fat % Calculator
Estimate your body fat percentage using the US Navy method — no equipment needed.
Body fat percentage is a far more meaningful measure of fitness than body weight alone, because it tells you what your weight is actually made of — fat versus lean tissue like muscle, bone, and organs. This calculator estimates your body fat percentage using the US Navy circumference method, which needs only a tape measure and a few body measurements, no expensive equipment or lab visit.
Two people can weigh exactly the same yet have very different bodies: one lean and muscular, the other carrying more fat. Tracking body fat percentage instead of (or alongside) the scale is especially valuable when you are exercising, because muscle gain can mask fat loss on the scale even as your composition clearly improves. This tool gives you a reasonable home estimate and a category interpretation so you can monitor real progress over time.
Plug in some numbers —
we'll crunch.
How to use
- 1Select your biological sex.
- 2Measure your height accurately.
- 3Measure your waist at the narrowest point (at the navel for men, smallest point for women).
- 4Measure your neck just below the larynx (Adam's apple).
- 5Women: also measure hip circumference at the widest point.
- 6Enter all measurements and click Calculate.
How it works
The US Navy method estimates body fat from circumference measurements rather than skinfold calipers or scans. For men it uses neck and waist measurements plus height; for women it adds the hip measurement, because fat distribution differs between sexes. These circumferences feed into a logarithmic formula that correlates surprisingly well with more expensive methods for most people.
The reason circumferences work is that fat accumulates in predictable areas — the waist for men, the waist and hips for women — so the ratio of those measurements to height proxies for overall fatness. The method is an estimate, typically accurate to within about 3–4 percentage points of a clinical measurement, which is plenty for tracking your own trend. General healthy ranges run roughly 10–20% for men and 18–28% for women, with athletes often lower.
Worked examples
A male estimate
A man who is 180 cm tall, with a 38 cm neck and an 85 cm waist.
- Measure neck and waist at the right points (snug, not compressing).
- Feed neck (38), waist (85), and height (180) into the Navy formula.
- The result lands around 15%.
An estimated 15% body fat places him in the 'fitness' range — lean and healthy, with visible muscle definition but not at competition-level leanness.
Why the scale can lie
Over two months of strength training, your weight holds at 75 kg.
- Body fat estimate drops from 22% to 19%.
- That is about 2.25 kg of fat lost (3% of 75 kg).
- Lean mass rose by roughly the same amount.
The scale showed zero progress, but you lost over 2 kg of fat and gained muscle. This is exactly why body fat percentage often tells a truer story than weight.
Tips & common mistakes
Measurement technique is everything with the Navy method. Use a flexible tape, keep it level and snug without compressing the skin, measure at the same points each time (waist at the navel, neck just below the larynx), and measure first thing in the morning for consistency. Small differences in where you place the tape can swing the result by a couple of percent.
Focus on the trend, not the absolute number. Because this is an estimate, the most reliable signal is the direction of change over weeks and months under consistent conditions — a steady decline means you are losing fat, regardless of whether the exact figure is off by a point or two. Take measurements under the same conditions every time to keep them comparable.
Do not chase extremely low body fat. Below roughly 5–8% for men and 12–15% for women, essential fat needed for hormones and organ function is at risk, which can harm health. The 'fitness' and 'athletic' ranges are healthy targets for most people. This calculator gives an estimate for general education only and is not a medical assessment — for clinical accuracy, a DEXA scan or professional evaluation is the gold standard, and any health decisions should involve a qualified professional.
Frequently asked questions
⚠ Estimated values only. DEXA scan or hydrostatic weighing provides clinical-grade accuracy.
Last reviewed: June 2026
About this calculator
Estimate your body fat percentage using the US Navy method — no equipment needed.