 Onbase percentage

In baseball statistics, onbase percentage (OBP) (sometimes referred to as onbase average [OBA], as the statistic is rarely presented as a true percentage) is a measure of how often a batter reaches base for any reason other than a fielding error, fielder's choice, dropped/uncaught third strike, fielder's obstruction, or catcher's interference (the latter two are ignored as either timesonbase (TOB) or plate appearances in calculating OBP). OBP is added to slugging average to determine onbase plus slugging (OPS). It first became an official MLB statistic in 1984.
Contents
Overview
Traditionally, the best leadoff hitters in the game have high onbase percentages. The league average for onbase percentage has varied considerably over time; in the modern era it is around .340, whereas it was typically only .300 in the deadball era. Onbase percentage can also vary quite considerably from player to player. The record for the highest career OBP by a hitter, based on over 3000 plate appearances, is .482 by Ted Williams. The lowest is by Bill Bergen, who had an OBP of .194.
For small numbers of atbats, it is possible (though unlikely) for a player's onbase percentage to be lower than his batting average (H/AB). This happens when a player has almost no walks or times hit by pitch, with a higher number of sacrifice flies (e.g. if a player has 2 hits in 6 at bats plus a sacrifice fly, his batting average would be .333, but his onbase percentage would be .286). The player who experienced this phenomenon with the most number of atbats in a season was Ernie Bowman, who over 125 atbats in 1963 had a batting average of .184 and an onbase percentage of .181.
Onbase percentage is calculated using this formula:
where
 H = Hits
 BB = Bases on Balls (Walks)
 HBP = times Hit By a Pitch
 AB = At bats
 SF = Sacrifice Flies
NOTE: Sacrifice flies were not counted as an official statistic until 1954. Before that time, all sacrifices were counted as sacrifice hits (SH), which included both sacrifice flies and bunts. Sacrifice bunts (sacrifice hits since 1954), which would lower a batter's onbase percentage, are not included in the calculation for onbase percentage, as bunting is an offensive strategy – often dictated by the manager – the use of which does not necessarily reflect on the batter's ability and should not be used to penalize him. For calculations of OBP before 1954, or where sacrifice flies are not explicitly listed, the number of sacrifice flies should be assumed to be zero.
Alltime leaders
bold is active player
Singleseason leaders
# Player OBP^{[2]} 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 See also
 List of MLB players with a .400 onbase percentage
 Moneyball: The Art of Winning an Unfair Game
Notes
 ^ "Career Leaders for On Base Percentage". Sports Reference, Inc. http://www.baseballreference.com/leaders/onbase_perc_career.shtml?redir. Retrieved 20110625.
 ^ "Single Season League Leaders for OnBase Percentage". Sports Reference, Inc.. http://www.baseballreference.com/leaders/onbase_perc_season.shtml. Retrieved 20110625.
Baseball statistics Batting Batting average • Onbase percentage • Slugging percentage • Hit – (Single • Double • Triple • Home run) • Grand slam • RBI • Gamewinning RBI • Bunt • Sacrifice bunt • Sacrifice fly
Baserunning Run • Stolen base • Stolen base percentage • Caught stealing
Pitching Win–loss record • Pitchers of record • Save • Hold • Earned run • ERA • Quality start • Complete game • Shutout • Wild pitch • Passed ball • Strikeout • WHIP
Fielding Sabermetrics Base runs • Extrapolated Runs • Isolated Power • Onbase plus slugging • Range factor • Runs created • Secondary average • Out of zone plays made • Ultimate zone rating • Weighted onbase average • Wins above replacement • Win probability added • Win shares
Team stats Sports league ranking
Categories: Baseball statistics
 Baseball terminology
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