baseball statistics Baseball statistics include a variety of metrics used to evaluate player and team performance in the sport of baseball. Because the flow of a baseball game has natural breaks to it, and player activity is characteristically distinguishable ind ...

, home runs allowed per nine innings pitched (HR/9IP or HR/9) or home runs allowed per nine innings (denoted by HR/9) is the average number of

home runs In baseball, a home run (abbreviated HR) is scored when the ball is hit in such a way that the batter is able to circle the bases and reach home plate safely in one play without any errors being committed by the defensive team. A home run ...

given up by a

pitcher In baseball, the pitcher is the player who throws ("Pitch (baseball), pitches") the Baseball (ball), baseball from the pitcher's mound toward the catcher to begin each play, with the goal of out (baseball), retiring a batter (baseball), batter, ...

per nine

innings pitched In baseball, the statistic innings pitched (IP) is the number of innings a pitcher has completed, measured by the number of Batter (baseball), batters and baserunners that have been put out while the pitcher is on the Baseball field#Pitcher's mou ...

. It is determined by multiplying the number of home runs allowed by nine and dividing by the number of innings pitched.What is a Home Runs Per Nine Innings (HR/9)? , Glossary , MLB.com
/ref> Pitchers with high fly ball rates are more likely than pitchers with high

ground ball In the sports of baseball and softball, a batted ball is a pitch that has been contacted by the batter's bat. Batted balls are either fair or foul, and can be characterized as a fly ball, pop-up, line drive, or ground ball. In baseball, a fou ...

rates to have high HR/9 rates.

Leaders

The career leaders in HR/9IP through 2018 were

Jim Devlin James Alexander Devlin (June 6, 1849 – October 10, 1883) was an American Major League Baseball (MLB) player who played mainly as a first baseman early in his career, then later as a pitcher. Devlin played for three teams during his five-ye ...

(0.0448),

Al Spalding Albert Goodwill Spalding (September 2, 1849 – September 9, 1915) was an American pitcher, manager, and executive in the early years of professional baseball, and the co-founder of the Spalding sporting goods company. He was born and raised ...

(0.0468), and

Reb Russell Ewell Albert "Reb" Russell (March 12, 1889 – September 30, 1973) was an American Major League Baseball player for the Chicago White Sox and the Pittsburgh Pirates. Career MLB Russell was drafted by the White Sox as a pitcher in 1912. In his ...

(0.0488). There were 87 single-season leaders in HR/9IP through 2018 who pitched a season without giving up a home run.Single-Season Leaders & Records for Home Runs per 9 IP , Baseball-Reference.com
/ref> All played before 1927. The active leaders in HR/9IP through 2018 were

Clayton Kershaw Clayton Edward Kershaw (born March 19, 1988) is an American professional baseball pitcher for the Los Angeles Dodgers of Major League Baseball (MLB). A left-handed starting pitcher, Kershaw has spent his entire MLB career with the Dodgers s ...

(0.6225),

Adam Wainwright Adam Parrish Wainwright (born August 30, 1981), nicknamed "Waino" and "Uncle Charlie", is an American former professional baseball pitcher who spent his entire 18-year Major League Baseball (MLB) career with the St. Louis Cardinals. The Atlanta ...

(0.6755), and Charlie Morton (0.7682).Active Leaders & Records for Home Runs per 9 IP , Baseball-Reference.com
/ref>

References

Pitching statistics {{baseball-stub