BMI can't tell muscle from fat — body fat percentage can. The US Navy method estimates it from simple tape measurements and is surprisingly accurate for a home tool (typically within 3–4% of lab methods). You'll need a soft tape measure and two minutes.
About this tool
Reference ranges (American Council on Exercise): Essential fat is about 10–13% for women and 2–5% for men; “fitness” sits around 21–24% (women) and 14–17% (men); average is 25–31% and 18–24%. Very low body fat carries its own health risks — more is not always worse, and less is not always better.
This tool is for general information and screening purposes only. It is not medical advice and cannot diagnose any condition. Always consult a qualified healthcare professional about your health.