In baseball statistics, Walks plus hits per inning pitched (WHIP) is a sabermetric measurement of the number of baserunners a pitcher has allowed per inning pitched. It is a general measure of a pitcher's ability to prevent batters from reaching base.
Along with on-base plus slugging (OPS) for hitters, WHIP is one of the few sabermetric statistics to enter mainstream baseball usage. It is one of the most commonly used statistics in fantasy baseball, and is standard in fantasy leagues that use the 4×4, 5×5, and 6×6 formats.
The lowest WHIP in baseball history was posted by Boston Red Sox pitcher Pedro Martínez in 2000. Martinez allowed 128 hits and 32 walks in 217 innings, for an 0.7373 ratio. Cleveland Indians right-hander Addie Joss holds the career record, with a 0.9678 WHIP in 2327 innings. However, Joss' career was cut short by meningitis at the age of 31, and thus he had no "decline phase." Chicago White Sox spitballer Ed Walsh is the only other pitcher with a career WHIP under 1.00, with a 0.9996 WHIP in 2964 innings. Pedro Martínez is third all-time with a career WHIP of 1.0306 as of early 2008, not counting Mariano Rivera's 1.03 in only 1003 innings, which is the best ever by a predominant relief pitcher. Among pitchers in the top 100 for innings pitched, the New York Giants' Christy Mathewson (1.0588 WHIP in over 4780 innings), and the Washington Senators workhorse Walter Johnson (1.0611 WHIP in more than 5914 innings) are well ahead of the pack.