Body Fat Estimator
Add body circumference measurements to calculate using the US Navy method, which is generally more accurate than the BMI-based estimate.
Enter your height, weight, age, biological sex to see your body fat estimate.
How It Works
This calculator estimates body fat percentage using two well-established methods. When both are available, the US Navy method is shown as the primary result because it accounts for body shape rather than just size.
US Navy Method
Developed by Hodgdon and Beckett in 1984, this method estimates body fat from circumference measurements. For men, it uses neck and waist measurements. For women, it adds hip circumference. These measurements are combined with height using a logarithmic formula to estimate body density, which is then converted to body fat percentage.
BMI-based Method
This formula converts your Body Mass Index into an estimated body fat percentage, adjusting for age and sex. While easier to calculate (it only needs height, weight, age, and sex), it can be less accurate for muscular individuals since BMI cannot distinguish between muscle and fat.
How to Measure
For the most accurate results with the US Navy method, follow these measurement guidelines:
- Neck - Measure just below the larynx (Adam's apple) with the tape sloping slightly downward to the front. Don't flare the neck outward.
- Waist - For men, measure at navel level. For women, measure at the narrowest point of the torso. Don't pull your stomach in while measuring.
- Hip - Measure at the widest horizontal point of the buttocks. Keep the tape level and parallel to the floor.
Use a soft measuring tape and stand naturally. Take each measurement twice and use the average for the most reliable result.
Limitations
Body fat calculators provide estimates, not precise measurements. Keep these limitations in mind:
- Measurement error - Small differences in where you place the tape can meaningfully change results. The Navy method has an error margin of approximately 3-4%.
- Individual variation - These formulas are based on population averages. Body fat distribution varies between individuals due to genetics, ethnicity, and other factors.
- BMI method limitations - The BMI-based formula cannot distinguish between muscle and fat. Muscular individuals will get inflated body fat estimates.
- More accurate methods exist - DEXA scans, hydrostatic weighing, and bioelectrical impedance analysis (BIA) provide more precise measurements, though they require equipment or professional administration.
- Not medical advice - This calculator is an educational tool. Consult a healthcare professional before making decisions based on body fat estimates, particularly around essential fat levels.