The method is popular because it needs only a tape measure, but accuracy is roughly plus or minus three percentage points, and it works best when measurements are taken carefully: at the navel for the waist, below the larynx for the neck, and at the widest point of the hips. Measure in the morning, un-flexed, and take the average of two readings.
Calculator
Formula used
Body fat % (Navy) = f(height, waist, neck[, hip]) · Fat mass = weight × body fat %
How to use the Body Fat Calculator
- Select your biological sex and preferred units.
- Enter height, weight and neck measurement.
- Add the waist, and the hip measurement for the female formula.
- Read your body fat percentage, fat mass and lean mass.
About this tool
The Body Fat Calculator is built for speed and accuracy: every calculation runs in your browser, so your data never leaves your device and the result updates as you type. It works equally well on a phone, a tablet or a desktop, and it is free to use as many times as you like.
Common use cases
- Tracking body composition during a cut or bulk.
- Checking progress alongside scale weight.
- Estimating lean body mass for protein targets.
- Comparing results against reference ranges.
Tips for the best result
- Use the latest figures you have - even a small change in rate or term can shift the outcome by hundreds.
- For annual figures, divide by 12 to get a monthly number you can compare with the result.
- Bookmark this page and revisit the calculation as the inputs change.
Frequently asked questions
How accurate is the Navy method?
Typically within about 3 percentage points of a DEXA scan for most people. Consistency matters more than absolute accuracy, so measure the same way each time.
Why is the result unrealistic?
Measurement error is the usual cause. Make sure the waist is measured at the navel, the neck below the larynx, and that the waist is larger than the neck.
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