- Start with 50 points.
- Add one point for each out recorded, so three points for every complete inning pitched.
- Add two points for each inning completed after the fourth.
- Add one point for each strikeout.
- Subtract two points for each hit allowed.
- Subtract four points for each earned run allowed.
- Subtract two points for each unearned run allowed.
- Subtract one point for each walk.
The maximum possible game score in a nine-inning game while allowing no baserunners is 114, possible only if a pitcher goes nine innings while striking out every batter he faces and facing three batters per inning. The pitcher receives 50 to begin with, and loses no points because there are no hits, walks, or runs of any kind. He receives 27 points for the 27 outs, and 10 points for five innings completed after the fourth inning, for a total of 87. In this "perfect score" scenario, the pitcher would have to strike out every hitter he faced, netting him an additional 27 points, for a grand total of 114.
The maximum possible score actually involves an extremely unlikely scenario in which three base runners reach base each inning on wild pitches or passed balls on third strikes. If this were to happen such that no one scored, and the pitcher recorded all outs by strikeout, a pitcher could theoretically record six strikeouts per inning, and thus 54 for the game, netting him 54 points in addition to the 87 he would have received as described above, for a total of 141.
Highest achieved scores
The highest game score for a nine-inning game in the history of baseball is Kerry Wood's one-hit, no walk, 20-strikeout shutout performance for the Chicago Cubs against the Houston Astros on May 6, 1998. His game score was 105 (50 + 27 + 10 + 20 – 2).
The highest game score for a no-hitter occurred on October 3rd, 2015, when Max Scherzer of the Washington Nationals allowed no hits and no walks, striking out 17, against the New York Mets. This is also the second-highest nine-inning game score in Major League Baseball history at 104 (50 + 27 + 10 + 17).
The 100th game score of 100 points or higher was pitched by Matt Cain in June 2012. Of the 100 such games, only ten of them were a regulation nine innings. Higher scores have been accomplished in extra-inning games. The two highest game scores ever recorded both occurred in the same game: the famous 26-inning duel from 1920, Joe Oeschger scored 153 and Leon Cadore scored 140. Oeschger had earlier scored a 102 in a 14-inning game in 1917 against Jeff Pfeffer, who scored 114. Oeschger's record in these games was 0-0, because both ended in ties and were called by darkness. In all, there have been nine games in which both starting pitchers scored 100 points; all required extra innings and none has occurred since 1971. Juan Marichal and Warren Spahn scored 112 and 97, respectively, during a complete game 16-inning match up; Spahn's score fell below 100 because of Willie Mays' game-winning home run in the bottom of the 16th.
21 pitchers with 100 or more game score points did so in losing games, including Harvey Haddix, who scored a 107 for the game in which he took a perfect game into the 13th inning. The highest-ever losing game score was 118, from Art Nehf, who outlasted the opposing starter by six innings but lost in the 21st inning. 17 of the 100+ game scores came in suspended tie games. Only seven of the 100 highest game scores were no-hitters.
Walter Johnson and Nolan Ryan had the most 100-point game scores with four apiece. Johnson had two in 1918, one in 1919, and a fourth in 1926; Ryan's came in 1972, 1973, 1990 and 1991. Warren Spahn had three 100-point game scores, in 1948, 1952 and 1960. Juan Marichal had three 100-point game scores, in 1963, 1966 and 1969. Eight pitchers had two 100-point game scores: Art Nehf (1917 and 1918), Joe Oeschger (1917 and 1920), Burleigh Grimes (1918 and 1920), Eric Erickson (1918 and 1921), Herb Pennock (1923 and 1925), Jim Maloney (1964 and 1965), Frank Tanana (1975 and 1976), and Max Scherzer (both 2015). 
Corey Kluber's game score of 98 in an eight-inning, no-run, one-hit, no-walk, 18-strikeout performance against the St. Louis Cardinals on May 13, 2015, is the highest by any pitcher in MLB history in a non-complete game. Indians bench coach Brad Mills removed him after the eighth inning, and Cody Allen pitched the ninth inning to seal a 2-0 win. The previous holder of the record was Matt Harvey, who achieved a game score of 97 for a nine-inning non-complete game against the Chicago White Sox. (Harvey's New York Mets won in ten innings.)
On June 18, 2014, Clayton Kershaw posted the 2nd highest ever game score for a 9-inning, no-hit effort. Kershaw struck out 15 while walking none, and the only baserunner was the result of a throwing error. His game score of 102 is the third-highest for a 9-inning game in MLB history (50 + 27 +10 + 15).
The lowest game score in baseball history was Allan Travers' 26-hit, 24-run start for the Detroit Tigers on May 18, 1912. His game score was a −52. This performance only came about because the regular Tiger players staged a strike in protest of Ty Cobb's suspension. To avoid a forfeit, local college players (including Travers) were enlisted as impromptu fill-ins. The lowest game score since 1957 was Oakland pitcher Mike Oquist's, who allowed 16 hits and 14 earned runs in five innings on August 3, 1998, for a −21.
The game score concept expands on Major League Baseball's official definition of a quality start. MLB defines a quality start as six or more innings pitched while allowing three or fewer earned runs. The game score system defines a quality start as a game score above 60.
The advantage that the system has over the official definition is that it allows a statistician a better view of the degree of quality in a pitcher's performance. Game scores can be quantified, and a pitcher's performance tracked over time. It is also possible to compare different pitchers. If one averages a 60 and another averages 55, presumably the first pitcher has had a better season.
In terms of high scores, the system favors current pitchers. It is difficult to achieve a very high score in a game without amassing a substantial number of strikeouts. In earlier eras, even for the very best pitchers, strikeouts were less plentiful. For instance, Cy Young's two no-hitters earned scores of just 90 and 88 due to their low strikeout totals (three and two, respectively). However, most of the all-time high game scores occurred in baseball's earlier era, when starting pitchers were permitted to remain in games longer than today; four of the top six all-time game scores were accomplished in stints of 21 innings or more.
Game scores of 100 in a 9-inning game
Thirteen times in Major League Baseball history, a pitcher has achieved a game score of 100 or higher in a 9-inning game.
|Pitcher||Team||Opposing team||Date||Game result||Game score||Line||Notes|
|Warren Spahn||Milwaukee Braves||Philadelphia Phillies||September 16, 1960||W 4-0||100||0 H, 2 BB, 15 K||No-hitter|
|Sandy Koufax||Los Angeles Dodgers||Chicago Cubs||September 9, 1965||W 1-0||101||0 H, 0 BB, 14 K||Perfect game|
|Nolan Ryan||California Angels||Boston Red Sox||July 9, 1972||W 3-0||100||1 H, 2 BB, 17 K|
|Nolan Ryan||California Angels||Detroit Tigers||July 15, 1973||W 6-0||100||0 H, 4 BB, 17 K||No-hitter|
|Nolan Ryan||Texas Rangers||Toronto Blue Jays||May 1, 1991||W 3-0||101||0 H, 2 BB, 16 K||No-hitter; Ryan's seventh and final no-hitter, a Major League Baseball record.|
|Kerry Wood||Chicago Cubs||Houston Astros||May 6, 1998||W, 2-0||105||1 H, 0 BB, 20 K||Tied for the Major League Baseball record for most strikeouts in a 9-inning game.|
|Curt Schilling||Arizona Diamondbacks||Milwaukee Brewers||April 7, 2002||W 2-0||100||1 H, 2 BB, 17 K|
|Randy Johnson||Arizona Diamondbacks||Atlanta Braves||May 18, 2004||W 2-0||100||0 H, 0 BB, 13 K||Perfect game.|
|Brandon Morrow||Toronto Blue Jays||Tampa Bay Rays||August 8, 2010||W 1-0||100||1 H, 2 BB, 17 K|
|Matt Cain||San Francisco Giants||Houston Astros||June 13, 2012||W 10-0||101||0 H, 0 BB, 14 K||Perfect game.|
|Clayton Kershaw||Los Angeles Dodgers||Colorado Rockies||June 18, 2014||W, 8-0||102||0 H, 0 BB, 15 K||No-hitter; Only batter to reach base was on a fielding error.|
|Max Scherzer||Washington Nationals||Milwaukee Brewers||June 14, 2015||W 4-0||100||1 H, 1 BB, 16 K|
|Max Scherzer||Washington Nationals||New York Mets||October 3, 2015||W 2-0||104||0 H, 0 BB, 17 K||No-hitter; highest game score achieved in a no-hitter. Only batter to reach base was on a throwing error in 6th inning. First occurrence of two 100-score games in a season by a pitcher.|
Career totals for some pitchers
The total number of game scores listed for each pitcher are starts in which he reached 90 points or higher. The parenthetical totals represent the highest score in the pitcher's career, and the number of game scores equal to or greater than 100 (if any). This is not a complete list and includes only pitchers with five or more games of 90 or higher (through 10/9/2015).
- May 13, 2015 St. Louis Cardinals at Cleveland Indians Box Score and Play by Play. Baseball-Reference.com (2013-05-13). Retrieved on 2015-05-14.
- May 7, 2013 Chicago White Sox at New York Mets Box Score and Play by Play. Baseball-Reference.com (2013-05-07). Retrieved on 2014-01-29.
- Corcoran, Cliff. (2013-05-07) Matt Harvey loses perfect game but accomplishes even rarer feat | The Strike Zone - SI.com. Mlb.si.com. Retrieved on 2014-01-29.
- Did you know? Kershaw's no-hitter MLB.com (2014-06-18). Retrieved on 2014-06-19.
- Pitching Game Finder. Baseball-Reference.com. Retrieved on 2014-01-29.