On base percentage - Definition and Overview

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. It may be calculated as:

(H + BB + HBP) / (AB + BB + HBP + SF)

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 and 5 at bats with a sacrifice fly, his batting average would be .400 but his on base percentage would be .333.