Inbaseball statistics,on-base percentage (OBP) measures how frequently abatter reachesbase. An officialMajor League Baseball (MLB) statistic since 1984, it is sometimes referred to ason-base average (OBA),[a] as it is rarely presented as a truepercentage.
Generally defined as "how frequently a batter reaches base perplate appearance",[1] OBP is specifically calculated as the ratio of a batter'stimes on base (the sum ofhits,bases on balls, and timeshit by pitch) to the sum ofat bats, bases on balls, hit by pitch, andsacrifice flies.[1] OBP does not credit the batter for reaching base onfielding errors,fielder's choice,uncaught third strikes,fielder's obstruction, orcatcher's interference, and deducts from plate appearances a batter intentionally giving himself up in asacrifice bunt.
OBP is added toslugging average (SLG) to determineon-base plus slugging (OPS).
The OBP of all batters faced by one pitcher or team is referred to as "on-base against".
On-base percentage is calculable for professional teams dating back to the first year ofNational Association of Professional Base Ball Players competition in 1871,[2] because the component values of its formula have been recorded inbox scores ever since.
The statistic was invented in the late 1940s byBrooklyn Dodgers statisticianAllan Roth with then-Dodgers general managerBranch Rickey.[3][4] In 1954, Rickey, who was then the general manager of thePittsburgh Pirates, was featured in aLife Magazine graphic in which the formula for on-base percentage was shown as the first component of an all-encompassing "offense" equation.[5] However, it was not named as on-base percentage, and there is little evidence that Roth's statistic was taken seriously at the time by the baseball community at large.[6]
On-base percentage became an official MLB statistic in 1984. Its perceived importance jumped after the influential 2003 bookMoneyball highlightedOakland Athletics general managerBilly Beane's focus on the statistic.[7] Many baseball observers, particularly those influenced by the field ofsabermetrics, now consider on-base percentage superior to the statistic traditionally used to measure offensive skill,batting average,[8][9] which accounts for hits but ignores other ways a batter can reach base.[10]
Traditionally, players with the best on-base percentages bat asleadoff hitter, unless they are power hitters, who traditionally bat slightly lower in thebatting order. The league average for on-base percentage inMajor League Baseball has varied considerably over time; at its peak in the late 1990s, it was around .340, whereas it was typically .300 during thedead-ball era. On-base percentage can also vary quite considerably from player to player. The highest career OBP of a batter with more than 3,000plate appearances is .482 byTed Williams. The lowest is byBill Bergen, who had an OBP of .194.
On-base percentage is calculated using this formula:[11][12][13]
where
In certain unofficial calculations, the denominator is simplified and replaced byPlate Appearance (PA); however, the calculation PAs includes certain infrequent events that will slightly lower the calculated OBP (i.e.catcher's interference, andsacrifice bunts).[13] Sacrifice bunts are excluded from consideration on the basis that they are usually imposed by the manager with the expectation that the batter will not reach base, and thus do not accurately reflect the batter's ability to reach base when attempting to do so. This is in contrast with the sacrifice fly, which is generally unintentional; the batter was trying for a hit.[1]
| # | Player | OBP[14] | Team(s) | Year(s) |
| 1 | Ted Williams | .4817 | Boston Red Sox | 1939–1942,1946–1960 |
| 2 | Babe Ruth | .4740 | Boston Red Sox,New York Yankees,Boston Braves | 1914–1935 |
| 3 | John McGraw | .4657 | Baltimore Orioles,St. Louis Cardinals,New York Giants | 1891–1906 |
| 4 | Billy Hamilton | .4552 | Kansas City Cowboys,Philadelphia Phillies,Boston Beaneaters | 1888–1901 |
| 5 | Lou Gehrig | .4474 | New York Yankees | 1923–1939 |
| 6 | Barry Bonds | .4443 | Pittsburgh Pirates,San Francisco Giants | 1986–2007 |
| 7 | Bill Joyce | .4349 | Brooklyn Ward's Wonders,Boston Reds,Brooklyn Grooms,Washington Senators, New York Giants | 1890–1898 |
| 8 | Rogers Hornsby | .4337 | St. Louis Cardinals, New York Giants, Boston Braves,Chicago Cubs,St. Louis Browns | 1915–1937 |
| 9 | Ty Cobb | .4330 | Detroit Tigers,Philadelphia Athletics | 1905–1928 |
| 10 | Jimmie Foxx | .4283 | Philadelphia Athletics, Boston Red Sox, Chicago Cubs, Philadelphia Phillies | 1925–1942,1944–1945 |
| 11 | Tris Speaker | .4279 | Boston Red Sox,Cleveland Indians,Washington Senators, Philadelphia Athletics | 1907–1928 |
| 12 | Eddie Collins | .4244 | Philadelphia Athletics,Chicago White Sox | 1906–1930 |
| # | Player | OBP[15] | Team | Year |
| 1 | Barry Bonds | .6094 | San Francisco Giants | 2004 |
| 2 | Barry Bonds | .5817 | San Francisco Giants | 2002 |
| 3 | Ted Williams | .5528 | Boston Red Sox | 1941 |
| 4 | John McGraw | .5475 | Baltimore Orioles | 1899 |
| 5 | Babe Ruth | .5445 | New York Yankees | 1923 |
| 6 | Babe Ruth | .5319 | New York Yankees | 1920 |
| 7 | Barry Bonds | .5291 | San Francisco Giants | 2003 |
| 8 | Ted Williams | .5256 | Boston Red Sox | 1957 |
| 9 | Billy Hamilton | .5209 | Philadelphia Phillies | 1894 |
| 10 | Babe Ruth | .5156 | New York Yankees | 1926 |
