Walks Plus Hits Per Inning Pitched

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 measure of a pitcher's ability to prevent batters from reaching base. The stat was invented in 1979 by Daniel Okrent.

While earned run average (ERA) measures the runs a pitcher gives up, WHIP more directly measures a pitcher's effectiveness against the batters faced. It is calculated by adding the number of walks and hits allowed and dividing this sum by the number of innings pitched; therefore, the lower a pitcher's WHIP, the better his performance. One key distinction between WHIP and ERA is that the former will continue to rise as long as batters reach base. If an error is committed with two outs in an inning, any runs scored beyond that point in the same inning will be considered unearned and will not cause that pitcher's ERA to rise. A WHIP of 1.0 or lower over the course of a season will often rank among the league leaders in Major League Baseball.

WHIP is one of the few sabermetric statistics to enter mainstream baseball usage. (On-base plus slugging, or OPS, a comparable measurement of the ability of a hitter, is another example.) It is one of the most commonly used statistics in fantasy baseball, and is standard in fantasy leagues that employ 4×4, 5×5, and 6×6 formats.

The lowest single-season WHIP in baseball history, 0.7373, was posted by Pedro Martínez, who was then with the Boston Red Sox, in 2000, breaking the previous MLB record of 0.77 by Guy Hecker of the Louisville Eclipse, even though he had less than 150 innings pitched that year, just like all-time MLB single-season ERA record holder Tim Keefe in 1880 (at 0.86 with 105 innings pitched). Cleveland Indians right-hander Addie Joss currently holds the record for the lowest career WHIP, with a 0.9678 WHIP in 2,327 innings. Chicago White Sox spitballer Ed Walsh ranks second, with a career WHIP under 1.00, with a 0.9996 WHIP in 2,964 innings, though it is the lowest career WHIP for a qualified pitcher with 10 or more seasons pitched. Providence Grays and New York Gothams right-hander John Ward is third all time with a career WHIP of 1.0440 (not counting right-handed closers Mariano Rivera, with a WHIP of 1.0012 in only 1,125 ⅔ innings, and Trevor Hoffman, with a WHIP of 1.0413 in 1,042 innings).