The Corpulence Index (CI) or Ponderal Index (PI) is a measure of leanness (corpulence) of a person[1] calculated as a relationship between mass and height.[2] It was first proposed in 1921 as the "Corpulence measure" by Swiss physician Fritz Rohrer[3][4] and hence is also known as Rohrer's Index.[5] It is similar to the body mass index, but the mass is normalized with the third power of body height rather than the second power.[6] It took almost a century after Rohrer proposed it, before Sultan Babar showed that CI does not need to be adjusted for height after adolescence.[4]