
In
baseball statistics
Baseball statistics include a variety of metrics used to evaluate player and team performance in the sport of baseball.
Because the flow of a baseball game has natural breaks to it, and player activity is characteristically distinguishable ind ...
, on-base percentage (OBP) measures how frequently a
batter reaches
base. An official
Major League Baseball
Major League Baseball (MLB) is a professional baseball league composed of 30 teams, divided equally between the National League (baseball), National League (NL) and the American League (AL), with 29 in the United States and 1 in Canada. MLB i ...
(MLB) statistic since 1984, it is sometimes referred to as on-base average (OBA), as it is rarely presented as a true
percentage
In mathematics, a percentage () is a number or ratio expressed as a fraction (mathematics), fraction of 100. It is often Denotation, denoted using the ''percent sign'' (%), although the abbreviations ''pct.'', ''pct'', and sometimes ''pc'' are ...
.
Generally defined as "how frequently a batter reaches base per
plate appearance
In baseball, a player is credited with a plate appearance (denoted by PA) each time he completes a turn batting. Under Rule 5.04(c) of the Official Baseball Rules, a player completes a turn batting when he is put out or becomes a runner. This ha ...
",
OBP is specifically calculated as the ratio of a batter's
times on base (the sum of
hits,
bases on balls
A base on balls (BB), better known as a walk,
occurs in baseball when a batter receives four pitches during a plate appearance that the umpire calls '' balls'', and is in turn awarded first base without the possibility of being called out. The bas ...
, and times
hit by pitch
In baseball, hit by pitch (HBP) is an event in which a batter or his clothing or equipment (other than his bat) is struck directly by a pitch from the pitcher; the batter is called a hit batsman (HB). A hit batsman is awarded first base, provide ...
) to the sum of
at bat
In baseball, an at bat (AB) or time at bat is a batter's turn batting against a pitcher. An at bat is different from a plate appearance. A batter is credited with a plate appearance regardless of what happens upon completion of his turn at bat, ...
s, bases on balls, hit by pitch, and
sacrifice flies.
OBP does not credit the batter for reaching base on
fielding errors,
fielder's choice
In baseball, fielder's choice (abbreviated FC) refers to a variety of plays involving an offensive player reaching a base due to the defense's attempt to put out another baserunner, or the defensive team's indifference to his advance. Fielder's c ...
,
uncaught third strikes,
fielder's obstruction, or
catcher's interference, and deducts from plate appearances a batter intentionally giving himself up in a
sacrifice bunt
In baseball, a sacrifice bunt (also called a sacrifice hit) is a batter's act of deliberately bunting the ball, before there are two outs, in a manner that allows a baserunner to advance to another base. The batter is almost always put out, a ...
.
OBP is added to
slugging average
In baseball statistics, slugging percentage (SLG) is a measure of the batting productivity of a hitter. It is calculated as total bases divided by at-bats, through the following formula, where ''AB'' is the number of at-bats for a given player, a ...
(SLG) to determine
on-base plus slugging
On-base plus slugging (OPS) is a sabermetric baseball statistic calculated as the sum of a player's on-base percentage and slugging percentage. The ability of a player both to get on base and to hit for power, two important offensive skills, are ...
(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 of
National Association of Professional Base Ball Players
The National Association of Professional Base Ball Players (NAPBBP), often known simply as the National Association (NA), was the first fully- professional sports league in baseball. The NA was founded in 1871 and continued through the 1875 se ...
competition in 1871, because the component values of its formula have been recorded in
box scores ever since.
History
The statistic was invented in the late 1940s by
Brooklyn Dodgers
The Brooklyn Dodgers were a Major League Baseball team founded in 1883 as the Brooklyn Grays. In 1884, it became a member of the American Association as the Brooklyn Atlantics before joining the National League in 1890. They remained in Brook ...
statistician
Allan Roth with then-Dodgers general manager
Branch Rickey. In 1954, Rickey, who was then the general manager of the
Pittsburgh Pirates
The Pittsburgh Pirates are an American professional baseball team based in Pittsburgh. The Pirates compete in Major League Baseball (MLB) as a member club of the National League (baseball), National League (NL) National League Central, Central ...
, was featured in a
Life Magazine
''Life'' (stylized as ''LIFE'') is an American magazine launched in 1883 as a weekly publication. In 1972, it transitioned to publishing "special" issues before running as a monthly from 1978 to 2000. Since then, ''Life'' has irregularly publi ...
graphic in which the formula for on-base percentage was shown as the first component of an all-encompassing "offense" equation. 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.
On-base percentage became an official MLB statistic in 1984. Its perceived importance jumped after the influential 2003 book ''
Moneyball Moneyball or money ball may refer to:
* '' Moneyball: The Art of Winning an Unfair Game'', 2003 book by Michael Lewis
** ''Moneyball'' (film), 2011 film adaptation of the book
* ''Moneyball'' (album), 2025 album by Dutch Interior
* Sabermetrics
...
'' highlighted
Oakland Athletics
The Oakland Athletics (frequently referred to as the Oakland A's) were an American Major League Baseball (MLB) team based in Oakland, California from 1968 to 2024. The Athletics were a member club of the American League (AL) American League We ...
general manager
Billy Beane
William Lamar Beane III (born March 29, 1962) is an American former professional baseball player and current Front office (sports), front office executive. He is currently senior advisor to owner John Fisher (baseball owner), John Fisher and ...
's focus on the statistic. Many baseball observers, particularly those influenced by the field of
sabermetrics
Sabermetrics (originally SABRmetrics) is the original or blanket term for sports analytics in the US, the empirical analysis of baseball, especially the development of advanced metrics based on baseball statistics that measure in-game activity ...
, now consider on-base percentage superior to the statistic traditionally used to measure offensive skill,
batting average
Batting average is a statistic in cricket, baseball, and softball that measures the performance of batters. The development of the baseball statistic was influenced by the cricket statistic.
Cricket
In cricket, a player's batting average is ...
, which accounts for hits but ignores other ways a batter can reach base.
Overview
Traditionally, players with the best on-base percentages bat as
leadoff hitter
In baseball, a leadoff hitter is a batter who bats first in the batting order (baseball), lineup. It can also refer to any batter who bats first in any inning.
Strategy
Traditionally, the leadoff hitter has been utilized as a contact-oriented ...
, unless they are power hitters, who traditionally bat slightly lower in the
batting order. The league average for on-base percentage in
Major League Baseball
Major League Baseball (MLB) is a professional baseball league composed of 30 teams, divided equally between the National League (baseball), National League (NL) and the American League (AL), with 29 in the United States and 1 in Canada. MLB i ...
has varied considerably over time; at its peak in the late 1990s, it was around .340, whereas it was typically .300 during the
dead-ball era
In major league baseball, the dead-ball era refers to a period from about 1900 to 1920 in which run scoring was low and home runs were rare in comparison to the years that followed. In 1908, the major league batting average dropped to .239, and ...
. On-base percentage can also vary quite considerably from player to player. The highest career OBP of a batter with more than 3,000
plate appearance
In baseball, a player is credited with a plate appearance (denoted by PA) each time he completes a turn batting. Under Rule 5.04(c) of the Official Baseball Rules, a player completes a turn batting when he is put out or becomes a runner. This ha ...
s is .482 by
Ted Williams
Theodore Samuel Williams (August 30, 1918 – July 5, 2002) was an American professional baseball player and manager. He played his entire 19-year Major League Baseball (MLB) career, primarily as a left fielder, for the Boston Red Sox from 193 ...
. The lowest is by
Bill Bergen, who had an OBP of .194.
On-base percentage is calculated using this formula:
:
where
*''H'' =
Hits
Hits or H.I.T.S. may refer to:
Arts, entertainment, and media Music
* '' H.I.T.S.'', 1991 album by New Kids on the Block
* ''...Hits'' (Phil Collins album), 1998
* ''Hits'' (compilation series), 1984–2006; 2014, a British compilation album s ...
*''BB'' =
Bases on Balls (Walks)
*''HBP'' =
Hit By Pitch
In baseball, hit by pitch (HBP) is an event in which a batter or his clothing or equipment (other than his bat) is struck directly by a pitch from the pitcher; the batter is called a hit batsman (HB). A hit batsman is awarded first base, provide ...
*''AB'' =
At bat
In baseball, an at bat (AB) or time at bat is a batter's turn batting against a pitcher. An at bat is different from a plate appearance. A batter is credited with a plate appearance regardless of what happens upon completion of his turn at bat, ...
*''SF'' =
Sacrifice fly
In certain unofficial calculations, the denominator is simplified and replaced by
Plate Appearance
In baseball, a player is credited with a plate appearance (denoted by PA) each time he completes a turn batting. Under Rule 5.04(c) of the Official Baseball Rules, a player completes a turn batting when he is put out or becomes a runner. This ha ...
(PA); however, the calculation PAs includes certain infrequent events that will slightly lower the calculated OBP (i.e.
catcher's interference, and
sacrifice bunt
In baseball, a sacrifice bunt (also called a sacrifice hit) is a batter's act of deliberately bunting the ball, before there are two outs, in a manner that allows a baserunner to advance to another base. The batter is almost always put out, a ...
s).
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.
All-time leaders
Single-season leaders
See also
*
*''
Moneyball: The Art of Winning an Unfair Game''
Notes
References
{{DEFAULTSORT:On-Base Percentage
Batting statistics
Baseball terminology
Percentages