Code for Calibrating a Reprap Printrbot

I have found many tutorials around the web showing how to calibrate Repraps and Printrbots. They tend to explain the technique very well, so I'll just let you Google that bit, but they often miss out the G code instructions.

To calibrate use this formula:

• (Steps per mm) * (expected distance traveled) / (actual distance traveled) 

Pronterface commands are as follows:

• M501 - show current settings (steps per mm)
• M92 X60 - change X steps per mm to 60 (interchangeable with X,Y,Z and E for Extruder)
• M500 - save new settings