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. WHIP is calculated by adding the number of walks and hits allowed and dividing this sum by the number of innings pitched.
WHIP reflects a pitcher's propensity for allowing batters to reach base, therefore a lower WHIP indicates better performance.
While earned run average (ERA) measures the earned runs a pitcher gives up, WHIP more directly measures a pitcher's effectiveness against batters.
History
The stat was invented in 1979 by writer Daniel Okrent,
WHIP is one of the few sabermetric statistics to enter mainstream baseball usage. The second-lowest single-season WHIP is held by Pedro Martínez of the 2000 Boston Red Sox with a WHIP of 0.7373; third-lowest single-season WHIP is held by Kenta Maeda of the 2020 Minnesota Twins, with a WHIP of 0.7500; the fourth-lowest single-season WHIP is held by the previously mentioned Guy Hecker; the fifth-lowest single-season WHIP is held by Walter Johnson of the 1913 Washington Senators, with a WHIP of 0.7803. Reliever Mariano Rivera ranks fourth among qualified pitchers with a career WHIP of 1.0003 in 1,283 innings.