Body Fat Percentage Calculator

Estimate your body fat percentage using the US Navy method with waist, neck and hip measurements.

Last updated: April 2026 · Source: NHS — Healthy weight

Disclaimer

This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.

How It Works

This calculator estimates body fat percentage using the US Navy method, which is based on circumference measurements. For men, you need neck and waist measurements; for women, neck, waist and hip measurements. The formula uses the logarithmic relationship between these measurements and height to estimate body fat.

Healthy body fat ranges vary by sex and age. For men, 10–20% is generally considered healthy; for women, 18–28%. Essential fat levels (below which health is compromised) are around 3–5% for men and 10–13% for women. Athletes typically sit at the lower end of the healthy range.

Measure at the narrowest point of the neck, the navel for waist (men) or the narrowest point (women), and the widest point for hips. Take measurements on bare skin, standing relaxed. For best accuracy, measure in the morning before eating. The Navy method has an accuracy of roughly ±3–4% compared to DEXA scans.

Example: Male, 180 cm, waist 88 cm, neck 38 cm

  1. Formula: 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
  2. log₁₀(88 − 38) = log₁₀(50) = 1.699
  3. log₁₀(180) = 2.255
  4. Body fat: 86.010 × 1.699 − 70.041 × 2.255 + 36.76 ≈ 18.6%

Source: NHS — Healthy weight

Frequently Asked Questions

What does the Body Fat Percentage Calculator do?
Estimate your body fat percentage using the US Navy method with waist, neck and hip measurements. All calculations are performed in your browser using official UK rates and thresholds.
Is this medical advice?
No. This calculator is for informational purposes only and does not constitute medical advice. Always consult your GP or an appropriate healthcare professional for medical guidance.
Are the reference values from the NHS?
Where applicable, this calculator uses reference values and guidelines from the NHS and other UK health authorities. Individual needs may vary based on personal health circumstances.