How it works
Choose a method and enter what it needs. With a tape measure, use US Navy or RFM. Without one, the BMI method works but is less accurate. The table compares every method that has enough data.
Formula
US Navy, men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
US Navy, women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hips − neck) + 0.22100 × log₁₀(height)) − 450
RFM: 64 (men) / 76 (women) − 20 × (height ÷ waist)
From BMI (Deurenberg): 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4 (men = 1, women = 0)
All measurements in centimetres.
FAQ
How do I measure waist, neck and hips?
Use a tape measure snug against the skin without squeezing. Measure the waist at the navel after a normal breath out, the neck just below the Adam's apple, and the hips at the widest point. Measuring in the morning before eating gives consistent results.
Which method is most accurate?
The tape (US Navy) and RFM methods are more accurate than the BMI method because they use waist size, which reflects belly fat. All of them are estimates within about 3–4%. For a precise value, use a DEXA scan or a body composition analyser.
What body fat % is normal?
By American Council on Exercise ranges, average is about 18–24% for men and 25–31% for women. Lower is fit or athletic. 25% and above for men and 32% and above for women counts as obese.
Why is body fat higher for women?
Women's bodies need more essential fat for hormones and fertility: about 10–13% for women versus 2–5% for men.