Body fat calculator

How to measure body fat with the Navy method

1. Select your sex: men need three measurements and women need four.
2. Measure your neck, waist, and (for women) hips with a flexible tape measure.
3. Enter your height to complete the formula inputs.
4. Your estimated body fat percentage and category appear instantly.

Common uses

• Tracking body composition changes during a cutting or bulking phase alongside a calorie calculator
• Assessing fitness level without expensive lab equipment alongside your BMI
• Checking whether you meet US Navy or military body fat standards

Technical specification

• Algorithm or formula: US Navy circumference method (Hodgdon & Beckett, 1984, Naval Health Research Center). Men: %BF = 495 / (1.0324 − 0.19077 · log10(waist − neck) + 0.15456 · log10(height)) − 450. Women: %BF = 495 / (1.29579 − 0.35004 · log10(waist + hip − neck) + 0.22100 · log10(height)) − 450. All measurements are in cm; inch inputs are multiplied by 2.54 first.
• Browser API or library: Native Math.log10. No external library.
• Input limits: Positive measurements in cm or inches, converted to cm before the log-arithmetic. A zero or negative value shows no result. The waist must be larger than the neck, and a result outside 0 to 75 percent shows a hint instead of a number.
• Output: Body-fat percentage, lean-mass percentage, and a category label (Essential fat, Athletic, Fitness, Average, Obese) using American Council on Exercise ranges.
• Known limitations: Population-derived formula validated mainly against US service personnel aged 18 to 55. Margin of error roughly ±3 to 4 percentage points versus hydrostatic weighing. Tape placement accuracy materially affects the result.

Frequently asked questions

What is a healthy body fat percentage?

The American Council on Exercise considers 14-24% healthy for men and 21-31% healthy for women. Athletes typically sit at 6-13% (men) or 14-20% (women), while essential fat is 2-5% and 10-13% respectively. The calculator uses the US Navy circumference method, which has an error of about three to four percentage points. Results are estimates for informational purposes only.

What is the US Navy body fat method?

The US Navy method estimates body fat percentage from circumference measurements using a logarithmic formula. Developed by Hodgdon and Beckett at the Naval Health Research Center in 1984 and validated against hydrostatic (underwater) weighing.

Do I need an account to use this calculator?

The calculator works without an account. Open the page and start entering measurements immediately. All calculations run in your browser. Our servers are not involved at any point.

How accurate is the Navy body fat method?

The method has a margin of error of approximately ±3–4 percentage points, comparable to skinfold caliper measurements and more practical than DEXA or hydrostatic weighing.