A Sabermertic statistic in baseball that measures a pitchers effectiveness at preventing batters from getting on base. The lower a pitchers WHIP, the better they are considered to be as they let fewer batters onto base, which suggests that they are more effective against batters.
Generally, the best pitchers in a season have a WHIP below 1.0.
WHIP = (Base on Balls (Walks) + Hits)/Innings Pitched
Walks Plus Hits Per Inning Pitched adds an additional insight into evaluating a pitchers along with stats like Earned Runs Against, Strikes and Strikeouts. The lowest single season WHIP was produced by Pedro Martinez in 2000 when he finished the season with a 0.7373 WHIP.