On-base percentage
In baseball statistics, on base percentage (OBP) 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:
OBP is sometimes referred to as "on base average" or OBA.
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.