Since we added Sean Smith's ("rallymonkey" to some) Wins Above Replacement measurement in 2010, we've seen its use expand in to many new areas and its popularity catch on in the media and the general population, but there have also been a lot of questions about how it's calculated and whether it has validity. In this tutorial, I'm going to run through the calculations in graphic detail and point out areas where our approach differs from some of the other popular WAR or WAR-like approaches.