View source for Adjusted ERA+

{{Short description|Baseball statistic}}
{{Missing information|who coined the term adjusted ERA+|date=September 2015}}
'''Adjusted ERA+''', often simply abbreviated to '''ERA+''' or '''ERA plus''', is a [[pitcher|pitching]] statistic in [[baseball]]. It adjusts a pitcher's [[earned run average]] (ERA) according to the pitcher's [[ballpark]] (in case the ballpark favors [[batter (baseball)|batters]] or pitchers) and the ERA of the pitcher's league.

==Formula==
ERA+ is calculated as:

<math>\mathit{ERA+} = 100 \cdot  {{\mathit{lgERA} \over \mathit{ERA}}} \cdot \mathit{PF}</math>

Where ERA is the pitcher's ERA, lgERA is the average ERA of the league, and PF is the [[Batting park factor|park factor]] of the pitcher in question.

This formula is now standard,<ref>{{cite web|title=Adjusted Earned Run Average (ERA+)|website=[[MLB.com]] |url=https://www.mlb.com/glossary/advanced-stats/earned-run-average-plus}}</ref> although [[Baseball-Reference.com]] briefly used a different formula which took values strictly between 0 and 200 instead of between 0 and infinity, but the current website shows values above 200 so it is clearly no longer in use:<ref>{{cite web|last1=Forman|first1=Sean|title=We Goofed: ERA+ numbers » Baseball-Reference Blog » Blog Archive|url=https://www.baseball-reference.com/blog/archives/5159|website=www.baseball-reference.com|access-date=1 August 2016}}</ref><ref>{{cite web|title=Esoteric Ramblings About +|date=28 March 2010 |url=http://walksaber.blogspot.com/2010/03/esoteric-ramblings-about.html}}</ref>

<math>\mathit{ERA+} = 100 \cdot (2 - {{\mathit{ERA} \over \mathit{lgERA}}} \cdot {{1 \over \mathit{PF}}})</math>

The average ERA+ is set to be 100; a score above 100 indicates that the pitcher performed better than average, while below 100 indicates worse than average. For instance, imagine the average ERA in the league is 4.00: if pitcher A has an ERA of 4.00 but is pitching in a ballpark that favors hitters, his ERA+ will be over 100. Likewise, if pitcher B has an ERA of 4.00 but pitches in a ballpark favoring pitchers, then his ERA+ will be below 100.

As a result, ERA+ can be used to compare pitchers across different run environments. In the above example, while ERA will lead one to believe that both pitchers pitched at the same level due to their ERAs being equivalent, ERA+ indicates that pitcher A performed better than pitcher B. ERA+ can thus be used to neutralize the effects of some well-known advantages and disadvantages on pitchers' ERA scores.

==Leaders==
[[Pedro Martínez]] holds the modern record for highest ERA+ in a single season; he posted a 1.74 ERA in the [[2000 in baseball|2000 season]] while pitching in the [[American League]], which had an average ERA of 4.92, which gave Martínez an ERA+ of 291.<ref>Single season awards require a minimum of one inning pitched for each game played (thus usually 162 IP in today's game).  Thus closers and other relievers will not generally acquire enough innings pitched to qualify.</ref>  While [[Bob Gibson]] has the lowest ERA in modern times (1.12 in the [[National League (baseball)|National League]] in [[1968 in baseball|1968]]), the average ERA was 2.99 that year (the so-called [[1968 Major League Baseball season#The Year of the Pitcher|Year of the Pitcher]]) and so Gibson's ERA+ is 258, eighth highest since 1900. 1968 was the last year that Major League Baseball employed the use of a [[pitcher's mound]] at {{convert|15|in}}, since {{convert|10|in}}.<ref>[http://en.allexperts.com/q/Baseball-Trivia-General-2552/2008/10/Pitchers-mound-1.htm Baseball Trivia (General) - Pitchers mound] {{Webarchive|url=https://web.archive.org/web/20090418195530/http://en.allexperts.com/q/Baseball-Trivia-General-2552/2008/10/Pitchers-mound-1.htm |date=2009-04-18 }}, allexperts.com.</ref>

The career record for ERA+ (with a minimum of 1,000 innings pitched) is held by [[Mariano Rivera]], a [[Closer (baseball)|closer]] whose career ERA+ is 205. Upon retirement in 2013, with an ERA+ of 194 in his final season, Rivera's career record of 205 surpassed the record among retired players of 154, held by Martínez, bumping [[Jim Devlin]], a pitcher in the 1870s, to third with 151.<ref>[https://www.baseball-reference.com/leaders/earned_run_avg_plus_career.shtml Baseball Reference career ERA+ leaders, accessed June 6, 2021. Also the source for the corresponding table.]</ref> Among qualifying pitchers, Pedro Martínez has the most separate seasons with an ERA+ over 200, with five, and the most consecutive 200 ERA+ seasons (4), though the closer Rivera, with too few innings each year to qualify officially, has surpassed 200 ERA+ in 13 seasons of his 19 seasons, including 4 consecutive seasons twice and 5 consecutive seasons once and also surpassing 300 in 2004 and again in 2008. [[Roger Clemens]] topped a 200 ERA+ three times, and [[Greg Maddux]] had two such seasons.

Players in '''bold''' are active as of the end of the [[2020 Major League Baseball season|2020 season]] and have not announced their retirement.

Single-season leaders include only pitchers eligible for the ERA title (a pitcher must throw a minimum of one inning per game scheduled for his team during the season to qualify for the ERA title).<ref>{{cite web |url=http://mlb.mlb.com/mlb/official_info/official_rules/official_scorer_10.jsp |title=Official Rules: 10.00 The Official Scorer |publisher=Major League Baseball |access-date=15 October 2016 }}</ref> Only pitchers with 1,000 or more innings pitched are shown in the career leader list.

{{Col-begin}}
{{Col-2}}
{| class="wikitable" style="font-size:98%;"
|+Career Leaders
! Rank !! Player !! Adjusted ERA+
|-
! 1
| [[Mariano Rivera]]        ||align="center" | 205
|-
! 2
| '''[[Clayton Kershaw]]''' ||align="center" | 157
|-
! 3
| '''[[Jacob deGrom]]'''    ||align="center" | 155
|-
! 4
| [[Pedro Martínez]]        ||align="center" | 154
|-
! 5
| [[Jim Devlin]]            ||align="center" | 150
|-
! 6
| [[Lefty Grove]]           ||align="center" | 148
|-
! rowspan=2 align="center" | T-7
| [[Walter Johnson]]
| align="center" rowspan=2 | 147
|-
| [[Hoyt Wilhelm]]
|-
! rowspan=3 align="center" | T-9
| [[Dan Quisenberry]]
| align="center" rowspan=3 | 146
|-
| [[Ed Walsh]]
|-
| [[Smoky Joe Wood]]
|-
! rowspan=2 align="center" | T-12
| [[Roger Clemens]]
| align="center" rowspan=2 | 143
|-
| [[Addie Joss]]
|-
! 14
| [[Brandon Webb]]          ||align="center" | 142
|-
! 15
| [[Trevor Hoffman]]        ||align="center" | 141
|-
! 16
| '''[[Chris Sale]]'''      ||align="center" | 140
|-
! 17
| [[Kid Nichols]]           ||align="center" | 139
|-
! rowspan=3 align="center" | T-18
| [[Mordecai Brown]]
| align="center" rowspan=3 | 138
|-
| [[John Franco]]
|-
| [[Cy Young]]
|-
! rowspan=3 align="center" | T-21
| [[Christy Mathewson]]
| align="center" rowspan=3 | 136
|-
| [[Johan Santana]]
|-
| [[Bruce Sutter]]
|-
! rowspan=4 align="center" | T-24
| [[Pete Alexander]]
| align="center" rowspan=4 | 135
|-
| [[Randy Johnson]]
|-
| '''[[Corey Kluber]]'''
|-
| [[Rube Waddell]]
|-
|}
{{Col-2}}
{|class="wikitable" style="font-size:98%;"
|+Single Season Leaders<ref>{{Cite web|title=Single-Season Leaders & Records for Adjusted ERA+|url=https://www.baseball-reference.com/leaders/earned_run_avg_plus_season.shtml|access-date=2020-11-20|website=Baseball-Reference.com|language=en}}</ref>
!Rank !!Player !!Adjusted ERA+ !!Year !!Team
|-
!1
|[[Tim Keefe]] ||align="center"|293 ||1880 ||[[Troy Trojans (MLB team)|Troy Trojans]]
|-
!2
|[[Pedro Martínez]] ||align="center"|291 ||2000 ||[[Boston Red Sox]]
|-
!3
|'''[[Shane Bieber]]''' ||align="center"|281 ||2020 ||[[Cleveland Indians]]
|-
!4
|[[Dutch Leonard (left-handed pitcher)|Dutch Leonard]] ||align="center"|279 ||1914 ||[[Boston Red Sox]]
|-
!5
|'''[[Trevor Bauer]]''' ||align="center"|276 ||2020 ||[[Cincinnati Reds]]
|-
|-
!6
|[[Greg Maddux]] ||align="center"|271 ||1994 ||[[Atlanta Braves]]
|-
!7
|[[Greg Maddux]] ||align="center"|260 ||1995 ||[[Atlanta Braves]]
|-
!8
|[[Walter Johnson]] ||align="center"|259 ||1913 ||[[History of the Washington Senators (1901–60)|Washington Senators]]
|-
!9
|[[Bob Gibson]] ||align="center"|258 ||1968 ||[[St. Louis Cardinals]]
|-
!10
|[[Mordecai Brown]] ||align="center"|253 ||1906 ||[[Chicago Cubs]]
|-
!rowspan=2| T-11
|[[Pedro Martínez]] || align="center" rowspan=2|243 ||1999 ||[[Boston Red Sox]]
|-
|[[Walter Johnson]] || 1912 || [[History of the Washington Senators (1901–60)|Washington Senators]]
|-
!13
|[[Christy Mathewson]] ||align="center"|233 ||1905 ||[[History of the New York Giants (NL)|New York Giants]]
|-
!14
|[[Dwight Gooden]] ||align="center"|229 ||1985 ||[[New York Mets]]
|-
!15
|[[Roger Clemens]] ||align="center"|226 ||2005 ||[[Houston Astros]]
|-
!16
|[[Grover Cleveland Alexander|Pete Alexander]] ||align="center"|225 ||1915 ||[[Philadelphia Phillies]]
|-
!rowspan=2| T-17
|[[Christy Mathewson]] ||align="center" rowspan=2|224 ||1909 ||[[History of the New York Giants (NL)|New York Giants]]
|-
|'''[[Dallas Keuchel]]''' || 2020 ||[[Chicago White Sox]]
|-
!rowspan=2| T-19
|[[Roger Clemens]] ||align="center" rowspan=2|222 ||1997 ||[[Toronto Blue Jays]]
|-
|'''[[Zack Greinke]]''' || 2015 || [[Los Angeles Dodgers]]
|}
{{Col-end}}

==References==
{{reflist}}

{{Baseball statistics}}

[[Category:Baseball statistics]]
[[Category:Major League Baseball statistics]]
[[Category:Pitching statistics]]