Body Mass Index (BMI) is a weight-to-height ratio. It’s useful for population screening, but it can’t distinguish muscle from fat — that’s why some athletes look “overweight” by BMI alone.
Body Fat % estimates fat relative to total mass and correlates better with health, performance, and aesthetics. Our Body Fat % calculator uses a validated BMI-based approximation with demographic adjustments to give you a quick estimate.
How to use them together
- Start with BMI for a fast check.
- If BMI feels off (e.g., you’re muscular), calculate body fat % for clarity.
- Add waist measurement and progress photos for context.
Try our calculators: BMI • Body Fat %.
Bottom line
Use BMI as a screening tool; use body fat % for decisions. The combination paints a more accurate picture of health and progress.