On Base Percentage (OBP) is the percentage of times a batter gets on base to the number of times they have been at the plate.
A higher OBP is a sign of a hitter that is more likely to advance bases.
It is an alternative to batting average. Compared with BA, OBP includes the number of times they have been walked or hit by a pitch, which are not normally included in statistics that rely only on upon “at bats.”
On Base Percentage (OBP) = (hits + walks + hit by pitch) ÷ (at-bats + walks + hit by pitch + sacrifice flies)
It is the number of times the batter advances to the number of times they have a chance to advance.
If a batter has been at bat 127 times and in that time has made: 32 hits, 7 walks, been hit by a pitch 2 times, and 3 sacrifice flies, then:
32 hits + 7 walks + 2 hit by a pitch = 41
127 at-bats + 7 walks + 2 hit by a pitch + 3 sacrifice flies = 139
41 ÷ 139 = 0.295
Therefore, the batter’s on-base percentage is 0.295.
Sources and more resources
- Wikipedia – On Base Percentage, Hit (Baseball), At bat, Base on Balls, Hit by Pitch, Sacrifice Fly, and Sacrifice Bunt – Wikipedia entries on the statistics used for OBP.
- Statistics on OBP from ESPN and Baseball-Reference.
- Rules on baseball and baseball statistics from Major League Baseball, NCAA (Baseball), NCAA (Softball), NCAA (Baseball and Softball), NFHS, and the International Baseball Federation.