On-Base Percentage

In baseball statistics, on-base percentage (OBP, sometimes OBA for "on-base average") is a measure of how often a batter reaches base for any reason other than a fielding error, fielder's choice, fielder's obstruction, or catcher's interference.

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

NOTE: Sacrifice flies were not counted as an official statistic until 1954. Before that time, all sacrifices were counted as sacrifice hits (SH), which included both sacrifice flies and bunts. Bunts (sacrifice hits since 1954), which would lower a batter's on-base percentage, are not included in the calculation for on-base percentage, as bunting is an offensive strategy – often dictated by the manager – the use of which does not necessarily reflect on the batter's ability and should not be used to penalize him. For calculations of OBP before 1954, or where sacrifice flies are not explicitly listed, the number of sacrifice flies should be assumed to be zero.

OBP became an official MLB statistic in 1984 and has gained popularity in TV broadcasts, often being displayed along with the player's Batting Average. OBP can be combined with slugging percentage to determine a player's OPS.