On-Base Percentage (OBP)

$$ OBP={\frac {HITS+WALKS+HIT\ BY\ PITCH}{AT\ BATS+WALKS+HIT\ BY\ PITCH+SACRIFICE\ FLY}} $$

The ratio of batter's times-on-base (the sum of hits, walks, and times hit by pitch) to number of plate appearances. On-base percentage measures how frequently a batter reaches base. It first became an official MLB statistic in 1984. Traditionally, players with the best on-base percentages bat as the leadoff hitter, unless they are power hitters, who normally bat slightly lower in the batting order.

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 (SLG) to determine on-base plus slugging (OPS).

Factoids

• The MLB record for highest career OBP by a hitter, based on over 3,000 plate appearances, is .482 by Ted Williams.

• The single season record OBP is held by Barry Bonds who achieved a .609 OBP with the San Francisco Giants in 2004. Bonds also holds the number two spot for OBP with .581 in 2002.