# On-base percentage

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 statistic generally measuring how frequently a batter reaches base.[1] Specifically, it records the ratio of the batter's times-on-base (TOB) (the sum of hits, walks, and times hit by pitch) to their number of plate appearances.[1] It first became an official MLB statistic in 1984.

By factoring in only hits, walks and times hit by pitch, OBP does not credit the batter for reaching base due to fielding errors or decisions, as it does not increase when the batter reaches base due to fielding error, fielder's choice, dropped/uncaught third strike, fielder's obstruction, or catcher's interference.

On-base percentage is added to slugging average to determine on-base plus slugging (OPS). The on-base percentage of all batters faced by one pitcher or team is referred to as on-base against.

## 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 in Major League Baseball 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. 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.

On-base percentage is calculated using this formula[2][3][4]:

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

where

In certain unofficial calculations, the denominator is simplified and replaced by Plate Appearance (PA); however, the calculation PAs includes certain infrequent events that will slightly lower the calculated OBP (i.e. catcher's interference, and sacrifice bunts).[4] 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.[1]

 # Player OBP[5] 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 Joey Votto .4277 Cincinnati Reds 2007-Present

bold is active player

 # Player OBP[6] 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