Body fat calculator
This needs a tape measure and nothing else. The US Navy method reads body fat from circumferences and height, which is why it is used where calipers and scanners are not available.
- Band
- Fitness
- Fat mass
- 29.8 lb
- Lean mass
- 140.2 lb
- Waist-to-height ratio
- 0.486
- Method
- US Navy
An estimate from circumference measurements, not a clinical body composition assessment. What a healthy figure is for you is a conversation with a clinician, not a formula.
The formula
Men: 86.010·log₁₀(waist − neck) − 70.041·log₁₀(height) + 36.76. Women: 163.205·log₁₀(waist + hip − neck) − 97.684·log₁₀(height) − 78.387. All measurements in inches; metric input is converted first.
Worked example
A man of 178 cm with a 38 cm neck and an 86 cm waist comes out at 17.3% — the fitness band — which on 77 kg is 13.3 kg of fat and 63.7 kg of lean mass.
How to use it
- 1Measure the waist at the navel, the neck just below the larynx, and the hips at the widest point. Keep the tape level and snug without compressing.
- 2Measure first thing in the morning, before eating, for consistency.
- 3Track the trend over months. A single reading carries three to four points of error; the direction over time is the real signal.
Questions people ask
How accurate is the tape method?
Within about three to four percentage points of a DEXA scan for most people, and less reliable at the extremes. It is good at detecting change and poor at pinning down an exact number.
What about waist-to-height ratio?
It is the simplest health screen there is: keeping your waist under half your height is the usual guideline, and it predicts cardiometabolic risk at least as well as BMI.
Last reviewed: 2026-10-20