Free tool
Body fat calculator (US Navy method)
Estimate your body fat percentage with a tape measure, no callipers or special scales needed.
Short answer: The US Navy method estimates body fat from height and neck and waist measurements, plus hips for women. It is usually within a few percentage points of lab methods. Measure the same way each time and track the trend.
- Estimated body fat
- 16.4%
- US Navy tape-measure method
- Fat mass
- 13.1 kg
- Lean (fat-free) mass
- 66.9 kg
- Use this in the FFMI calculator
Tape-measure estimates are typically within a few percentage points of lab methods, so use the same tape, the same spots and the same time of day, and watch the trend rather than one reading. This is an estimate, not a medical assessment. Nothing you enter is saved or sent anywhere.
How the US Navy body fat method works
US Navy researchers measured body fat by underwater weighing and found that height, neck and waist (and hips for women) predicted it well. The equations they published are still used by the US military (Hodgdon & Beckett, 1984).
How to measure with a tape measure
Use a flexible tape, keep it level and snug but not pressing into the skin, and breathe out normally before reading the waist. Measure twice and use the average. Take readings in the morning before eating for the most consistent results.
How accurate is it?
Like every home method, it is an estimate. It can read high for people with a lot of muscle around the neck and low or high for people who carry fat in unusual places. Its real value is tracking change over time with the same method.
What to do with the result
Put your lean mass into the FFMI calculator to see how muscular you are for your height, or use the fat-loss timeline calculator if you want to get leaner. This is not a medical assessment; speak to your GP about any health concern.
Scientific sources
More endurance tools and guides: Sports nutrition, including the race fuelling and hydration calculator.
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Educational information for adults aged 18 and over. It does not diagnose, treat or manage any medical condition. If you have a health condition, or symptoms that worry you, speak to your doctor or a health professional.