Body Fat Calculator
Estimate your body fat percentage
About the Body Fat Calculator
The Body Fat Calculator estimates your body fat percentage from a few tape-measure readings, using the US Navy circumference method. It is a quick alternative to calipers or a body-composition scale.
How it works
For men, body fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. For women, it is 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. The formula uses inches, so the tool converts your centimetre measurements first.
How to Use Body Fat Calculator
Enter Your Data
Select your sex and measure your waist (at the navel), neck and height in cm.
Run the Tool
Women also measure the hips at their widest point.
Use the Result
Press Calculate to see your estimated body fat percentage.
Why Use Our Body Fat Calculator?
100% Free
No registration, no hidden fees, no limits — ever.
Privacy First
All processing runs in your browser. Your data never leaves your device.
Mobile Friendly
Works perfectly on phones, tablets, and desktops.
Instant Results
Results appear as soon as you run the tool.
Frequently Asked Questions
Q. How accurate is the Navy method?
Studies typically find it within about 3–4 percentage points of lab methods like DEXA. Measure consistently, at the same time of day, for the best comparisons over time.
Q. What is a healthy body fat percentage?
The American Council on Exercise lists roughly 14–24% as average for men and 21–31% for women, with athletes lower.
Q. Why does it need my neck measurement?
Neck size is used as a proxy for lean mass, which helps separate muscle from fat at the waist.