baseball Baseball is a bat-and-ball sport played between two teams of nine players each, taking turns batting and fielding. The game occurs over the course of several plays, with each play generally beginning when a player on the fielding t ...

earned run average In baseball statistics, earned run average (ERA) is the average of earned runs allowed by a pitcher per nine innings pitched (i.e. the traditional length of a game). It is determined by dividing the number of earned runs allowed by the numb ...

(ERA) is a

statistic A statistic (singular) or sample statistic is any quantity computed from values in a sample which is considered for a statistical purpose. Statistical purposes include estimating a population parameter, describing a sample, or evaluating a hypo ...

used to evaluate

pitcher In baseball, the pitcher is the player who throws ("pitches") the baseball from the pitcher's mound toward the catcher to begin each play, with the goal of retiring a batter, who attempts to either make contact with the pitched ball or dr ...

s, calculated as the

mean There are several kinds of mean in mathematics, especially in statistics. Each mean serves to summarize a given group of data, often to better understand the overall value ( magnitude and sign) of a given data set. For a data set, the '' ar ...

of earned runs given up by a pitcher per nine

innings pitched In baseball, innings pitched (IP) are the number of innings a pitcher has completed, measured by the number of batters and baserunners that are put out while the pitcher is on the pitching mound in a game. Three outs made is equal to one inning ...

. A pitcher is assessed an earned run for each run scored by a

baserunner In baseball, base running is the act of running from base to base, performed by members of the team at bat. Base running is a tactical part of the game with the goal of eventually reaching home base (home plate) to score a run. Batters strive t ...

who reached base while batting against that pitcher, whether by

hit Hit means to strike someone or something. Hit or HIT may also refer to: Arts, entertainment and media Fictional entities * Hit, a fictional character from '' Dragon Ball Super'' * Homicide International Trust, or HIT, a fictional organization ...

, base on balls or "walk", or being hit by a pitched ball; an earned run can be charged after the pitcher is relieved if he allows the runner before leaving the game. Runs scored by players who reach base on

errors An error (from the Latin ''error'', meaning "wandering") is an action which is inaccurate or incorrect. In some usages, an error is synonymous with a mistake. The etymology derives from the Latin term 'errare', meaning 'to stray'. In statistics ...

passed ball In baseball, a catcher is charged with a passed ball when he fails to hold or control a legally pitched ball that, with ordinary effort, should have been maintained under his control, and, as a result of this loss of control, the batter or a ru ...

s, or

catcher interference In baseball, interference occurs in situations in which a person illegally changes the course of play from what is expected. Interference might be committed by players on the offense, players not currently in the game, catchers, umpires, or spec ...

under special circumstances are treated as unearned runs, and do not count towards the pitcher's ERA.

Major League Baseball Major League Baseball (MLB) is a professional baseball organization and the oldest major professional sports league in the world. MLB is composed of 30 total teams, divided equally between the National League (NL) and the American League (A ...

recognizes the player in each league with the lowest earned run average each season. The first ERA champion in the National League was George Bradley; in the National League's inaugural 1876 season, Bradley posted a 1.23 ERA for the

St. Louis Brown Stockings The St. Louis Brown Stockings were a professional baseball club based in St. Louis, Missouri, from 1875 to 1877, which competed on the cusps of the existences of two all-professional leagues—the National Association (NA) and the National Leagu ...

, allowing 78 earned runs in 573 innings pitched. The American League was established in 1901, and

Hall of Fame A hall, wall, or walk of fame is a list of individuals, achievements, or other entities, usually chosen by a group of electors, to mark their excellence or fame in their field. In some cases, these halls of fame consist of actual halls or muse ...

pitcher

Cy Young Denton True "Cy" Young (March 29, 1867 – November 4, 1955) was an American Major League Baseball (MLB) pitcher. Born in Gilmore, Ohio, he worked on his family's farm as a youth before starting his professional baseball career. Young entered th ...

led that league with a 1.62 ERA for the Boston Americans during the 1901 season. Over the course of his 17-year major league career, Lefty Grove led the American League in ERA nine times, with a career single-season low of 2.06 for the 1931

Philadelphia Athletics The Philadelphia Athletics were a Major League Baseball team that played in Philadelphia from 1901 to 1954, when they moved to Kansas City, Missouri, and became the Kansas City Athletics. Following another move in 1967, the team became the Oakla ...

Roger Clemens William Roger Clemens (born August 4, 1962), nicknamed "Rocket", is an American former professional baseball pitcher who played 24 seasons in Major League Baseball (MLB), primarily with the Boston Red Sox. Clemens was one of the most dominant pi ...

has won the second-most ERA titles, capturing six in the American League and one in the National League. Sandy Koufax led the National League in ERA for five consecutive seasons (1962–1966); Koufax' five awards are the most won consecutively by any player and are tied for the most awards by a player in the National League with Christy Mathewson and Clayton Kershaw. In the American League, Walter Johnson also won five ERA titles, and Pedro Martínez has won a total of five (four American League and one National League) with two different teams. The most recent ERA champions are Justin Verlander in the American League and Julio Urías in the National League. The lowest single-season ERA in league history was posted by

Tim Keefe Timothy John Keefe (January 1, 1857 – April 23, 1933), nicknamed "Smiling Tim" and "Sir Timothy", was an American Major League Baseball pitcher. He stood tall and weighed . He was one of the most dominating pitchers of the 19th century and po ...

, whose 0.86 ERA in 105 innings pitched for the National League's

Troy Trojans The Troy Trojans are the sports teams of Troy University. They began playing in the NCAA's Division I-A in 2001, became a football only member of the Sun Belt Conference in 2004, and joined that conference for all other sports in 2005. Troy Unive ...

in 1880 led his closest competitor by .52 runs. In the American League, Dutch Leonard's 0.96 ERA is a single-season record. Keefe and Leonard are the only two pitchers ever to allow less than one run per nine innings pitched in a single season. The widest margin of victory for an ERA champion is 1.96 runs, achieved when Martínez' 1.74 ERA led Clemens' 3.70 in the American League during the 2000 season. The largest margin of victory in the National League is 1.26 runs— Dazzy Vance's 2.61 ERA over

Carl Hubbell Carl Owen Hubbell (June 22, 1903 – November 21, 1988), nicknamed "the Meal Ticket" and "King Carl", was an American Major League Baseball player. He was a pitcher for the New York Giants of the National League from 1928 to 1943, and remained o ...

's 3.87 in 1930. The smallest margin of victory for an ERA champion is .009 runs. Although the statistic is traditionally recorded to two decimal places by most the 1988 American League title was decided by a margin of less than one hundredth of a run when Allan Anderson's ERA of 2.446 (55 earned runs in innings) bested Teddy Higuera's 2.455 mark (62 earned runs in innings). Other contests decided by one hundredth or less include Luis Tiant's 1.91 ERA ahead of Gaylord Perry's 1.92 in 1972 and Mark Fidrych (2.34) over Vida Blue (2.35) in 1976.

Key

National League

Notes

* While Baseball-Reference.com lists both Niekro and

Joaquín Andújar Joaquín Andújar (; December 21, 1952 – September 8, 2015) was a Dominican professional baseball pitcher who played in Major League Baseball (MLB) for the Houston Astros, St. Louis Cardinals, and Oakland Athletics from 1976 through 19 ...

with an ERA of 2.47 in 1982, Niekro's average is lower (2.467) than Andújar's (2.473) if extended to three decimal places.

American League

Notes

* While Baseball-Reference.com lists both Scarborough and Hall of Famer

Bob Lemon Robert Granville Lemon (September 22, 1920 – January 11, 2000) was an American right-handed pitcher and manager in Major League Baseball (MLB). Lemon was elected to the National Baseball Hall of Fame in 1976. Lemon was raised in Californi ...

with an ERA of 2.82 in 1948, Scarborough's average is lower (2.817) than Lemon's (2.820) if extended to three decimal places. * While Baseball-Reference lists both Anderson and Higuera with an ERA of 2.45 in 1988, Anderson's average is lower (2.446) than Higuera's (2.455) if extended to three decimal places. * Until 1981, the rules stated that the number of innings pitched should be rounded to the nearest whole inning. This explains why McCatty was, at the time, awarded the 1981 ERA title although his ERA appears to be slightly higher than that of Stewart.

Footnotes

* This is shown in the mathematical formula at right. *Recognized "major leagues" include the current

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

and

National League The National League of Professional Baseball Clubs, known simply as the National League (NL), is the older of two leagues constituting Major League Baseball (MLB) in the United States and Canada, and the world's oldest extant professional team s ...

s and several defunct leagues—the

American Association American Association may refer to: Baseball * American Association (1882–1891), a major league active from 1882 to 1891 * American Association (1902–1997), a minor league active from 1902 to 1962 and 1969 to 1997 * American Association of Profe ...

, the Federal League, the

Players' League The Players' National League of Professional Base Ball Clubs, popularly known as the Players' League (PL), was a short-lived but star-studded professional American baseball league of the 19th century. The PL was formed by the Brotherhood of Prof ...

, and the Union Association. * A pitcher must average throwing at least one inning per game scheduled for his team during the season (currently 162 innings per 162 games) to qualify for the ERA title.

References

;General * * ;Inline citations {{featured list ERA champions

Key

National League

Notes

American League

Notes

Footnotes

See also

References