Body Fat Calculator
Estimate body fat percentage using the U.S. Navy formula.
Body fat percentage gives a more complete picture of body composition than weight or BMI alone, distinguishing between lean muscle mass and stored fat. This calculator uses the US Navy method, requiring just a few body measurements to estimate your body fat percentage without specialised equipment.
Estimated body fat will appear here...
How to Estimate Your Body Fat Percentage
- Select your gender — the Navy formula uses different equations for males and females due to differences in fat distribution.
- Measure your height — stand straight against a wall and measure in centimetres. Accuracy matters here.
- Measure your neck circumference — wrap a tape measure around the narrowest part of your neck, just below the larynx.
- Measure your waist — for males, measure at navel height. For females, measure at the narrowest point of your torso.
- Measure your hips (females only) — measure at the widest point of your hips and buttocks.
- Click Calculate — the tool applies the U.S. Navy formula and returns your estimated body fat percentage.
Frequently Asked Questions
How does the U.S. Navy body fat formula work? ▼
The Navy method uses circumference measurements (neck, waist, and hips for women) along with height to estimate body fat. It applies logarithmic equations that correlate these proportions with body composition. While not as precise as DEXA scans, it is reliable and widely used by the U.S. military for fitness assessments.
What is a healthy body fat percentage? ▼
For men, 10–20% is considered a healthy range, with 6–13% being athletic. For women, 18–28% is healthy, and 14–20% is athletic. Essential fat minimums are roughly 2–5% for men and 10–13% for women — going below these levels is dangerous.
How accurate is the Navy method compared to DEXA? ▼
Studies show the Navy method is accurate within about 3–4% of DEXA scan results for most people. It tends to be less accurate for very lean or very overweight individuals. For tracking trends over time, it is highly consistent and practical.
Why is body fat percentage better than BMI? ▼
BMI only considers weight and height, so it cannot distinguish between muscle and fat. A muscular athlete and an overweight sedentary person can have the same BMI. Body fat percentage directly measures fat proportion, giving a much better picture of body composition and health risk.
How often should I measure body fat? ▼
Measure every 2–4 weeks under the same conditions (same time of day, same hydration level). Body fat changes slowly, so weekly measurements often just show normal fluctuation rather than real trends.
Is my measurement data stored anywhere? ▼
No. All calculations happen in your browser. Your measurements are never sent to a server or stored in any database.