http://en.wikipedia.org/wiki/Walks_p...inning_pitched
Walks plus hits per inning pitched (WHIP) is a sabermetric measurement of how many baserunners a pitcher is responsible for allowing per inning pitched. It gives a general measure of a pitcher's ability to keep batters off base. A WHIP of 1.15 or below will often rank among the best in Major League Baseball.
As indicated by the name, it is calculated by adding the number of walks plus hits allowed divided by the number of innings pitched.
http://www.baseball-reference.com/le...P_career.shtml