BMI (body mass index)
BMI is weight in kilograms divided by height in metres squared. It was designed to describe populations, not individuals, and it cannot distinguish muscle from fat or say anything about where body fat sits.
Example
A muscular athlete and a sedentary person of the same height and weight have the same BMI and very different body composition. This site uses BMI internally where a formula requires it, and deliberately publishes no BMI landing page.