# On-base percentage

(Redirected from On base average)

In baseball statistics, on-base percentage (OBP; sometimes referred to as on-base 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 times-on-base (TOB) or plate appearances in calculating OBP). OBP is added to slugging average to determine on-base plus slugging (OPS). It first became an official MLB statistic in 1984.

## Overview

Traditionally, players with the best on-base percentages bat as leadoff hitter, unless they are power hitters, who traditionally bat slightly lower in the batting order. 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. 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 appearances, is .482 by Ted Williams. The lowest is by Bill Bergen, 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 (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 on-base percentage would be .286). The player who experienced this phenomenon with the most number of at-bats over a full season was Ernie Bowman. In 1963, with over 125 at-bats, Bowman had a batting average of .184 and an on-base percentage of .181.

On-base percentage is calculated using this formula:

$OBP = \frac{H+BB+HBP}{AB+BB+HBP+SF}$

where

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 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.

 # Player OBP[1] 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, Philadelphia Athletics 1906–1930

bold is active player