Body Fat Calculator
Body fat percentage is a more direct measure of body composition than BMI, since it separates fat mass from lean mass. This calculator uses the US Navy circumference method, which requires only a measuring tape.
Fill in the form and select Calculate to see your result here.
What is Body Fat?
The US Navy method estimates body fat percentage from circumference measurements at the neck, waist and (for women) hips, combined with height. It is not as precise as lab methods like DEXA scans but is far more accessible and reasonably reliable for tracking change over time.
Body Fat Formula
The formula uses the logarithmic relationship between waist-to-neck (and hip, for women) ratios and body fat percentage, calibrated against US Navy personnel data.
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
Body Fat Example
A man who is 175 cm tall with a 38 cm neck and 85 cm waist would have his measurements plugged into the formula above to estimate body fat percentage, typically landing in the "Fitness" or "Average" range depending on the exact numbers.
General Body Fat Categories
| Category | Men | Women |
|---|---|---|
| Essential Fat | 2-5% | 10-13% |
| Athletes | 6-13% | 14-20% |
| Fitness | 14-17% | 21-24% |
| Average | 18-24% | 25-31% |
| Obese | 25%+ | 32%+ |
How to Use This Calculator
- Select your gender.
- Measure your neck, waist and (if female) hip circumference in centimetres using a flexible measuring tape.
- Enter your height and measurements above.
- Select "Calculate" to see your estimated body fat percentage and category.
Limitations
- Measurement accuracy strongly affects the result — measure at the same time of day, without clothing compression, for consistency.
- This method is less accurate for individuals with atypical body shapes or very high or low body fat.
- For clinical-grade accuracy, methods like DEXA scans or hydrostatic weighing are more precise.