Body Fat Calculator Estimate body fat percentage using the US Navy method with waist, neck, and hip measurements.
Body Fat Calculator
Estimate body fat percentage using the US Navy method with waist, neck, and hip measurements.
Select Units & Sex
Choose metric or imperial and your biological sex.
Enter Measurements
Input weight, height, waist, neck, and hip (females) circumferences.
View Body Fat Results
See your body fat percentage, fat mass, lean mass, and fitness category.
What Is Body Fat Calculator?
The Body Fat Calculator estimates your body fat percentage using the US Navy circumference method, a validated approach that uses body measurements to approximate body composition. For males, it uses waist and neck circumference relative to height. For females, it also includes hip circumference. This method is accurate to within 3-4% of more expensive methods like DEXA scans. Body fat percentage is a more meaningful health indicator than weight alone or BMI, as it distinguishes between fat mass and lean mass. The calculator also shows your fitness category based on established body fat percentage ranges for your sex.
Why Use Body Fat Calculator?
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Uses the validated US Navy body fat estimation method
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More informative than BMI — separates fat mass from lean mass
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Shows fitness category (athlete, fitness, average, above average)
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Requires only a tape measure — no expensive equipment needed
Common Use Cases
Fitness Assessment
Track body composition changes during fitness programs.
Military/Service Requirements
The US Navy method is used for military body composition standards.
Weight Loss Tracking
Monitor fat loss while ensuring lean mass is preserved.
Health Screening
Body fat percentage is a better indicator of metabolic health than BMI alone.
Technical Guide
The US Navy body fat formula uses circumference measurements and height in a logarithmic equation. For males: BF% = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For females: BF% = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. All measurements should be in centimeters. Waist is measured at the narrowest point (navel level for males). Neck is measured just below the larynx. Hip is measured at the widest point. The formula has a typical error of ±3-4% compared to hydrostatic weighing and DEXA scans.
Tips & Best Practices
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1Measure at the same time of day for consistency — morning is best
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2Use a cloth tape measure and keep it snug but not tight
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3Take multiple measurements and average them for accuracy
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4Track trends over weeks rather than focusing on single readings
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🔢 Math & CalculatorsFrequently Asked Questions
Q How accurate is the US Navy method?
Q What is a healthy body fat percentage?
Q Where should I measure my waist?
Q Is body fat better than BMI?
Q How often should I measure body fat?
About This Tool
Body Fat Calculator is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.