Body Fat Calculator
Estimate your body fat percentage with simple tape measurements. See your lean mass, fat mass, and body composition category — more meaningful than BMI.
- Neck: Measure at the narrowest point, just below the Adam's apple
- Waist: Measure at the navel level, relaxed (don't suck in)
Estimated body fat
24%
Average
Understanding Body Fat Percentage
The US Navy Method
Developed by Hodgdon and Beckett in 1984, the US Navy method estimates body fat from circumference measurements. It's the standard used by the US Department of Defense for military fitness assessments. The formula uses neck and waist measurements for men, and neck, waist, and hip measurements for women, along with height.
Studies show it's accurate within 3-4% of DEXA scan results for most people — good enough for tracking trends over time, which is what matters most for fitness progress.
Body Fat vs BMI
BMI (Body Mass Index) is calculated from just height and weight. It can't distinguish between muscle and fat. A 200lb person who is 6 feet tall has a BMI of 27.1 (“overweight”) regardless of whether they're a bodybuilder at 12% body fat or sedentary at 30% body fat. Body fat percentage tells you what your weight is actually made of.
How to Get Accurate Measurements
- Measure in the morning before eating, for consistency
- Use a flexible tape measure (not a rigid ruler)
- Pull the tape snug but don't compress the skin
- Measure each site twice and take the average
- Stand relaxed — don't flex or suck in your stomach
Tracking Changes Over Time
The absolute number matters less than the trend. If your body fat goes from 22% to 18% over 3 months while your weight stays the same, you've gained muscle and lost fat — even if the scale hasn't moved. This is why body composition tracking is more valuable than scale weight alone.
Track your body composition journey
Ellim tracks your workouts, nutrition, and body measurements together — so you can see the full picture of your progress.
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