Body Fat Calculator
Estimate your body fat percentage with the US Navy method.
All calculations happen locally in your browser — nothing is uploaded, stored or tracked.
Choose your sex
The formula differs for men and women.
Enter measurements
Height, neck, waist (and hips for women), in cm or inches.
Read the estimate
Body fat %, fat mass, lean mass and category.
What Is a Body Fat Calculator?
Body fat percentage is the share of your weight that is fat. The US Navy method estimates it from a few circumference measurements — height, neck and waist (plus hips for women). It is a practical, no-equipment approach used by the US military, accurate to within a few percent for most people.
The calculator reports body fat percentage, fat mass, lean mass and the general category ranges (athletic, fit, average, above average).
The US Navy Formula
Measurements are in centimetres. Measure the waist at the navel, the neck below the larynx, and the hips at the widest point.
Limitations
Your data never leaves your device.
Every calculation on this site runs in your browser using vanilla JavaScript. Nothing is uploaded, stored or tracked.
- 100% local, client-side calculations
- No data stored on any server
- No tracking, no analytics, no ads scripts
- Works offline once loaded
Frequently Asked Questions
How is body fat percentage calculated?
The US Navy method uses a formula based on height, neck, waist (and hip for women) circumference — the calculator applies it for you.
What is a healthy body fat percentage?
Roughly 15–20% for men and 20–25% for women is often cited as a healthy range, but healthy ranges vary with age and goals.
How accurate is the Navy method?
Within a few percentage points of hydrostatic weighing for most people, with larger error at extremes of fitness or weight.
Do I need special equipment?
No — only a tape measure. That is the appeal of the circumference method.
What is lean body mass?
Everything that is not fat: muscle, bone, organs, water. It is weight minus fat mass.