How it works
The U.S. Navy method uses body circumferences and height to estimate body fat. It needs only a tape measure and is usually within 3–4% of lab methods.
Use it to track change
Measure the same way every 2–4 weeks: same time of day, same places, relaxed. The trend matters more than one number. Save your results in My progress.
What is FFMI
Fat-free mass index is lean mass divided by height squared. It shows how much muscle you carry for your height. Most trained people are between 19 and 23.
Questions and answers
What is a healthy body fat percentage?
Many sources use about 14–24% for men and 21–31% for women as a typical healthy range. Very low levels are not healthy to keep.
Why is my result different from my smart scale?
Scales use electrical impedance, which changes with water and food. Each method has its own error. Compare results from the same method over time.
How it is calculated: sources
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, 1984.
- American Council on Exercise (ACE). Percent body fat norms.
- Kouri EM et al. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med. 1995;5(4):223–228.
Gymvert gives general information for healthy adults. It is not medical advice. If you have a health condition, are pregnant, or are unsure, talk to a doctor before changing your training or diet.