Body Fat Calculator
Want a quick body fat estimate? Enter neck, waist, hips, and height and you will get your percentage with the US Navy method. No lab needed.
TL;DR
- The US Navy method uses neck, waist, and hip measurements with height.
- US Navy Formula Equations: Men: %Fat = 86.010 × log10(Waist - Neck) - 70.041 × log10(Height) + 36.76
- Example: Male Adult Measurement — Height: 178 cm, Waist: 84 cm, Neck: 38 cm, Total Weight: 80 kg
How it works
The US Navy method uses neck, waist, and hip measurements with height. A logarithmic formula turns those numbers into body fat percentage.
The math
The formula uses log ratios of waist to neck or waist plus hip minus neck, compared to height.
All measurements must be in centimeters (or scaled accordingly in inches). Subtracting neck circumference compensates for natural skeletal frame thickness.
Examples
Example: Male Adult Measurement
- Height: 178 cm, Waist: 84 cm, Neck: 38 cm, Total Weight: 80 kg
- Waist - Neck difference: 84 - 38 = 46 cm (33.07 - 14.96 = 18.11 in)
- Apply log10 terms: 86.010 × log10(18.11) - 70.041 × log10(70.08) + 36.76
- Calculation: (86.010 × 1.2579) - (70.041 × 1.8456) + 36.76 = 108.19 - 129.27 + 36.76 = 15.68%
- Body Fat: 15.7% | Lean Mass: 67.5 kg | Fat Mass: 12.5 kg.
When to use it
✦ Tracking Body Recomposition Progress
Monitor whether weight loss comes from fat loss rather than muscle tissue reduction.
✦ Establishing Health Category Baselines
Classify body composition into Essential Fat, Athletes, Fitness, Acceptable, or Obesity categories.
✦ Non-Invasive Personal Tracking
Avoid expensive hydrostatic weighing tanks or DEXA scans with reliable home measuring tape readings.
⚠ Common mistakes
- Sucking in the Stomach: Pulling in your stomach distorts waist measurements and gives artificially low fat readings.
- Inconsistent Tape Tension: Pulling the tape too tightly compresses subcutaneous fat; keep tape flat and level.
FAQ (2)
What is a healthy body fat percentage for men and women?
For men, 10-20% is typical for fitness and health. For women, 18-28% is optimal.
How often should I measure my body fat?
Measuring every 2 to 4 weeks provides clear trends without daily water retention fluctuations.
Sources & References
⚠ Health Disclaimer
This tool provides estimates for informational purposes only and does not constitute medical, veterinary, or professional advice. Always consult a qualified healthcare professional before making decisions about your health or treatment.