Taking anthropometrics data from DraftExpress and NBA.com I was able to find 921 players that measured for the combine (or another place) for their actual “barefoot” or “without shoes” height and then their listed height on NBA.com.
In doing so I found that the average height increase was 1.18 inches with the max increase being 2.75 inches. The minimum increase was 0.25 inches or just rounding up to the next height.
To be fair, the data was mostly on players from 2000-01 forward so it might not necessarily be conclusive to if we exaggerate player’s heights more today than during the 1960’s and 1970’s where there is some debate to protect the accomplishments of the likes of Wilt Chamberlain and Bill Russell. As the argument goes they played against midgets then vs now.
The 10 biggest exaggerated heights are listed here: