Body Fat Calculator
Estimate body fat % (U.S. Navy method).
100% private — runs in your browser, nothing is uploaded.
Body fat
10.1%
Athletes
Fat mass
8.1 kg
Lean mass
71.9 kg
Uses the U.S. Navy circumference method. It's an estimate, not a clinical measurement. Not medical advice.
How to use the Body Fat Calculator
- 1Pick sex and units
Choose male/female and metric or imperial.
- 2Measure and enter
Add height, neck and waist (and hips for women).
- 3Add your weight
Enter weight so fat mass and lean mass can be shown.
- 4Read your estimate
See your body fat percentage, category and mass breakdown.
Examples
| Input | Output |
|---|---|
Male · 178cm · neck 38 · waist 85 | ≈ 18% body fat — Fitness |
Free body fat percentage calculator
This body fat calculator estimates your body fat percentage using the U.S. Navy circumference method— a formula that needs only a tape measure and a few measurements. It's a practical way to track body composition at home, where scales and BMI fall short.
Why body fat beats the bathroom scale
Weight alone can't tell muscle from fat, and neither can BMI. Two people at the same height and weight can have very different body compositions. Estimating body fat percentage splits your weight into fat mass and lean mass, which is what actually matters for fitness and health goals.
Measure well for the best estimate
Accuracy depends on good measurements: keep the tape snug but not tight, level around the body, and measure the neck below the larynx and the waist at the navel (men) or narrowest point (women). Track the same way each time and the trend will be reliable even if any single reading is a little off. Everything is calculated privately in your browser — this is an estimate, not medical advice.
Frequently Asked Questions
How does the U.S. Navy body fat method work?
It estimates body fat from a few tape measurements — height, neck and waist (plus hips for women) — using a formula the U.S. Navy validated against more precise methods. No special equipment beyond a tape measure is needed.
How accurate is it?
For most people it lands within about 3–4% of a hydrostatic or DEXA measurement, which is remarkably good for a tape-only method. It's a useful trend tracker, not a clinical diagnosis.
Where exactly do I measure?
Measure your neck just below the larynx, your waist at the navel (men) or the narrowest point (women), and, for women, the hips at the widest point. Keep the tape snug and level, and don't hold your breath in.
What is a healthy body fat percentage?
Rough guides: men 10–20% and women 18–28% are typical 'fitness to average' ranges. Athletes sit lower. Essential fat (the minimum for health) is about 2–5% for men and 10–13% for women.
Why is body fat better than BMI?
BMI only uses height and weight, so it can mislabel a muscular person as overweight. Body fat percentage distinguishes fat from lean mass, giving a more meaningful picture of body composition.
Is my data private?
Yes. The estimate is calculated in your browser and nothing you enter is uploaded. It's not a substitute for professional medical advice.