On base percentage
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In baseball statistics, on base percentage (OBP) (sometimes referred to as on base average (OBA)) is a measure of how often a batter gets to first base for any reason other than a fielding error or a fielder's choice. OBP is part of the equation for determining on-base plus slugging.
The league average for on base percentage has varied considerably over time: in the modern era it is around .340, whereas it was only .300 in the dead-ball era. On base percentage can also vary quite considerably from player to player. The record for the highest OBP by a career hitter, adjudged to be over 5000 plate appearances, is .481 by Ted Williams. The lowest, however, is .265 by Hobe Ferris, although this was during the dead-ball era.
Though extremely unlikely, it is possible for a player's on base percentage to be lower than his batting average (H/AB). If a player had 2 hits in 5 at bats with a sacrifice fly, his batting average would be .400, but his on base percentage would be .333.
To calculate on base percentage (OBP) use this formula from the Major League Baseball site.
- <math>OBP = \frac{H+BB+HBP}{AB+BB+HBP+SF}</math>
where
- H = Hits
- BB = bases on balls
- HBP = Hit by pitch
- AB = At bats
- SF = Sacrifice flies