wRC+ takes the statistic Runs Created and adjusts that number to account for important external factors -- like ballpark or era. It's adjusted, so a wRC+ of 100 is league average and 150 would be 50 percent above league average.
For example, a player who plays his home games at hitter-friendly Coors Field will have a lower wRC+ than a player who posts identical stats at pitcher-friendly Oakland Coliseum.
(((wRAA per PA + league runs per PA) + (league runs per PA - ballpark factor x league runs per PA) / league wRC per plate appearance, not including pitchers)) x 100.
Why it's useful
>wRC+ quantifies run creation and normalizes it, so we can compare players who play in different ballparks and even different eras.