Body Fat Calculator

Estimate your body fat percentage using the U.S. Navy circumference method. Free body fat calculator for men and women with fitness category guidance.

This body fat calculator estimates your body fat percentage using the U.S. Navy circumference method — a validated formula that uses neck, waist, and (for women) hip measurements along with height. Unlike BMI, which only looks at weight and height, the Navy method distinguishes fat from lean mass, making it a better screening tool for people with more muscle. It requires only a flexible tape measure, not expensive equipment like calipers or DEXA scans. The calculator handles male and female formulas automatically based on the sex you select. While the Navy method is a practical and well-researched estimate, it is not as precise as a DEXA scan or hydrostatic weighing — but it is free, private, and takes under a minute. All calculations run in your browser and your measurements are never stored.

body

measurements

Result

-432.2
Body fat below 5% is dangerously low. Verify your measurements.

About Body Fat Calculator

What is body fat calculator?

This body fat calculator estimates your body fat percentage using the U.S. Navy circumference method — a validated formula that uses neck, waist, and (for women) hip measurements along with height. Unlike BMI, which only looks at weight and height, the Navy method distinguishes fat from lean mass, making it a better screening tool for people with more muscle. It requires only a flexible tape measure, not expensive equipment like calipers or DEXA scans. The calculator handles male and female formulas automatically based on the sex you select. While the Navy method is a practical and well-researched estimate, it is not as precise as a DEXA scan or hydrostatic weighing — but it is free, private, and takes under a minute. All calculations run in your browser and your measurements are never stored.

How to use this calculator

  1. Enter your sex.
  2. Enter your height.
  3. Enter your neck circumference.
  4. Enter your waist circumference.
  5. Enter your hip circumference (women).
  6. Click the "Calculate" button.
  7. View your result instantly — the main result is displayed prominently at the top with a detailed breakdown below it.

When to use this calculator

  • Estimating body fat percentage with only a tape measure
  • Tracking body composition changes during a fitness or weight-loss program
  • Getting a more nuanced health picture than BMI alone provides
  • Comparing body fat readings against healthy ranges for your sex and age
  • Screening for obesity-related health risks beyond what weight alone shows

How the calculation works

The U.S. Navy method uses different regression formulas for men and women. For men: body fat % = 495 / (1.0324 − 0.19077 × log₁₀(waist_cm − neck_cm) + 0.15456 × log₁₀(height_cm)) − 450. For women: body fat % = 495 / (1.29579 − 0.35004 × log₁₀(waist_cm + hip_cm − neck_cm) + 0.22100 × log₁₀(height_cm)) − 450. The constants were derived from large-scale anthropometric studies of U.S. Navy personnel and are validated against hydrostatic weighing — the gold standard for body composition measurement. Measurements should be taken with a flexible tape measure at standard anatomical sites: neck at the Adam's apple, waist at the navel (men) or narrowest point (women), and hips at the widest point. The formula computes body density first, then converts density to body fat percentage using the Siri equation.

Frequently Asked Questions

How does the Navy method estimate body fat?▼
It uses circumference measurements (neck, waist, and hip for women) plus height in a validated formula. It's a practical alternative to calipers or DEXA.
What is a healthy body fat percentage?▼
For men, 10-20% is generally healthy; for women, 18-28%. Essential fat minimums are about 2-5% for men and 10-13% for women.

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