On base percentage

# On base percentage

Discussion
 Ask a question about 'On base percentage' Start a new discussion about 'On base percentage' Answer questions from other users Full Discussion Forum

Encyclopedia
In baseball statistics
Baseball statistics
Statistics play an important role in summarizing baseball performance and evaluating players in the sport.Since the flow of a baseball game has natural breaks to it, and normally players act individually rather than performing in clusters, the sport lends itself to easy record-keeping and statistics...

, on-base percentage (OBP) (sometimes referred to as on-base average [OBA], as the statistic is rarely presented as a true percentage
Percentage
In mathematics, a percentage is a way of expressing a number as a fraction of 100 . It is often denoted using the percent sign, “%”, or the abbreviation “pct”. For example, 45% is equal to 45/100, or 0.45.Percentages are used to express how large/small one quantity is, relative to another quantity...

) is a measure of how often a batter
Batting (baseball)
In baseball, batting is the act of facing the opposing pitcher and trying to produce offense for one's team. A batter or hitter is a person whose turn it is to face the pitcher...

reaches base for any reason other than a fielding error
Error (baseball)
In baseball statistics, an error is the act, in the judgment of the official scorer, of a fielder misplaying a ball in a manner that allows a batter or baserunner to reach one or more additional bases, when such an advance would have been prevented given ordinary effort by the fielder.The term ...

, fielder's choice
Fielder's choice
In baseball, fielder's choice is a term used to refer 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...

, dropped/uncaught third strike, fielder's obstruction
Obstruction (baseball)
In baseball, when a fielder illegally hinders a baserunner, the fielder is guilty of obstruction.Baserunners are generally permitted the free privilege to run from base to base without being physically blocked or hindered by a fielder...

, or catcher's interference (the latter two are ignored as either times-on-base (TOB)
Times on base
In baseball statistics, the term times on base, also abbreviated as TOB, is the cumulative total number of times a batter has been awarded for reaching base as a result of hits, walks and hit by pitches. This stat does not include times reaching first by way of error, dropped 3rd strike, fielders...

or plate appearance
Plate appearance
In baseball statistics, a player is credited with a plate appearance each time he completes a turn batting. A player completes a turn batting when: He strikes out or is declared out before reaching first base; or He reaches first base safely or is awarded first base ; or He hits a fair ball which...

s in calculating OBP). OBP is added to slugging average to determine on-base plus slugging
On-base plus slugging
On-base plus slugging is a sabermetric baseball statistic calculated as the sum of a player's on-base percentage and slugging percentage. The ability of a player to both get on base and to hit for power, two important hitting skills, are represented. An OPS of .900 or higher in Major League...

(OPS). It first became an official MLB statistic in 1984.

## Overview

Traditionally, the best leadoff hitters in the game have high on-base percentages. The league average for on-base percentage has varied considerably over time; in the modern era it is around .340, whereas it was typically only .300 in the dead-ball era
The dead-ball era is a baseball term used to describe the period between 1900 and the emergence of Babe Ruth as a power hitter in 1919. In 1919, Ruth hit a then league record 29 home runs, a spectacular feat at that time.This era was characterized by low-scoring games and a lack of home runs...

. On-base 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 appearance
Plate appearance
In baseball statistics, a player is credited with a plate appearance each time he completes a turn batting. A player completes a turn batting when: He strikes out or is declared out before reaching first base; or He reaches first base safely or is awarded first base ; or He hits a fair ball which...

s, is .482 by Ted Williams
Ted Williams
Theodore Samuel "Ted" Williams was an American professional baseball player and manager. He played his entire 21-year Major League Baseball career as the left fielder for the Boston Red Sox...

. The lowest is by Bill Bergen
Bill Bergen
William Aloysius "Bill" Bergen was a Major League Baseball catcher in the early 20th century. Bergen was born in North Brookfield, Massachusetts on June 13, 1878...

, who had an OBP of .194.

For small numbers of at-bats, it is possible (though unlikely) for a player's on-base percentage to be lower than his batting average
Batting average
Batting average is a statistic in both cricket and baseball that measures the performance of cricket batsmen and baseball hitters. The two statistics are related in that baseball averages are directly descended from the concept of cricket averages.- Cricket :...

(H/AB). This happens when a player has almost no walks
Base on balls
A base on balls is credited to a batter and against a pitcher in baseball statistics when a batter receives four pitches that the umpire calls balls. It is better known as a walk. The base on balls is defined in Section 2.00 of baseball's Official Rules, and further detail is given in 6.08...

or times hit by pitch
Hit by pitch
In baseball, hit by pitch , or hit batsman , is a batter or his equipment being hit in some part of his body by a pitch from the pitcher.-Official rule:...

, with a higher number of sacrifice flies
Sacrifice fly
In baseball, a sacrifice fly is a batted ball that satisfies four criteria:* There are fewer than two outs when the ball is hit.* The ball is hit to the outfield....

(e.g. if a player has 2 hits in 6 at bats plus a sacrifice fly, his batting average would be .333, but his on-base percentage would be .286). The player who experienced this phenomenon with the most number of at-bats in a season was Ernie Bowman
Ernie Bowman
Ernest Ferrell Bowman is a former Major League Baseball infielder. Bowman played for the San Francisco Giants from to . He batted and threw right-handed....

, who over 125 at-bats in 1963 had a batting average of .184 and an on-base percentage of .181.

On-base percentage is calculated using this formula:

where
• H = Hits
Hit (baseball)
In baseball statistics, a hit , also called a base hit, is credited to a batter when the batter safely reaches first base after hitting the ball into fair territory, without the benefit of an error or a fielder's choice....

• BB = Bases on Balls (Walks)
Base on balls
A base on balls is credited to a batter and against a pitcher in baseball statistics when a batter receives four pitches that the umpire calls balls. It is better known as a walk. The base on balls is defined in Section 2.00 of baseball's Official Rules, and further detail is given in 6.08...

• HBP = times Hit By a Pitch
Hit by pitch
In baseball, hit by pitch , or hit batsman , is a batter or his equipment being hit in some part of his body by a pitch from the pitcher.-Official rule:...

• AB = At bat
At bat
In baseball, an at bat or time at bat is used to calculate certain statistics, including batting average, on base percentage, and slugging percentage. It is a more restricted definition of a plate appearance...

s
• SF = Sacrifice Flies
Sacrifice fly
In baseball, a sacrifice fly is a batted ball that satisfies four criteria:* There are fewer than two outs when the ball is hit.* The ball is hit to the outfield....

NOTE: Sacrifice flies were not counted as an official statistic until 1954
1954 in baseball
-Major League Baseball:* World Series: New York Giants over Cleveland Indians * All-Star Game, July 13 at Municipal Stadium: American League, 11-9-Other champions:* Caribbean World Series: Caguas Creoles [Criollos de Caguas]...

. Before that time, all sacrifices were counted as sacrifice hit
Sacrifice hit
In baseball, a sacrifice bunt is a batter's act of deliberately bunting the ball in a manner that allows a runner on base to advance to another base. The batter is almost always sacrificed but sometimes reaches base due to an error or fielder's choice...

s (SH), which included both sacrifice flies and bunts. Sacrifice bunts (sacrifice hits since 1954), which would lower a batter's on-base percentage, are not included in the calculation for on-base 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.