About a year ago I created an Advanced Statistics Calculator for my general NBA Blog, the Pick and Scroll. Unfortunately, there are only so many hours in a day, and I decided to focus solely on writing about the Kings and for StR.
You may have noticed a new picture on the sidebar of a calculator (the one up on top). If you click it, it will take you to the new home of the Advanced Stats Calculator on StR. Using it is very simple; Insert the raw stats from the game(s) you want and click calculate and you get your result.
Advanced Statistics can be very useful when you want to go in deeper analysis on a game or how a player/team played. Basketball-Reference has a nice glossary explaining what the Advanced Statistics in the calculator actually are in case you don't know.
Enjoy.
P.S. Before you ask, I cannot create a calculator for PER. It is an incredibly complicated formula and beyond my programming skill. However, I may add John Hollinger's Game Score, a simplified version of PER, at a later date.