What is On Base Percentage?
On Base Percentage (OBP) is a baseball statistic used to put a batter’s number of times they get on base in comparison to the number of times they have been at the plate.
It is intended to be a more accurate representation of a batter’s ability to get on base than their batting average – as it includes statistics such as the number of times they have been walked or hit by a pitch, which are normally not included in statistics that rely only on “at bats”.
How to calculate OBP
In Baseball, on base percentage is calculated as follows:
On Base Percentage (OBP) = (hits + walks + hit by pitch) / (at bats + walks + hit by pitch + sacrifice flies)
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 is 41.
127 at bats + 7 walks + 2 hit by a pitch + 3 sacrifice flies is 139.
41 divided by 139 is 0.295
Therefore, the batter’s on base percentage is 0.295.
What qualifies as a hit?
A hit is recorded when the batter safely reaches first base after hitting the ball into fair territory without the benefit of an error or a fielder’s choice.
If the batter (or runner) attempts another base and is caught out, they are still credited with the hit as long as they have reached 1st base.
What qualifies as a walk?
A walk occurs when the pitcher has thrown 4 balls before throwing 3 strikes or having the ball hit into play.
What qualifies as a “hit by pitch”?
A batter is hit by a pitch when the ball hits the batter during the pitching sequence.
What qualifies as a sacrifice fly?
A sacrifice fly happens when there are less than 2 outs and the ball is hit into outfield fair or foul territory or to infield foul territory.
If the batter is put out because a fielder catches the ball on the fly, an a runner who is already on base scores on the play, it counts as a sacrifice fly.
It should be noted that sacrifice bunts do not count against a batter’s calculation for on-base percentage like sacrifice flies are.
What qualifies as an “At Bat”?
An “at bat” is counted each time the player is at bat. At bats are not counted in specific circumstances, including:
- The batter being hit by a pitch
- Sacrifice fly or sacrifice hit
- Base on balls
- Inning ends while still at bat
- The batter is replaced by another hitter before the turn is completed
- Wikipedia – On Base Percentage
- Wikipedia – Hit (Baseball)
- Wikipedia – At bat
- Wikipedia – Base on Balls
- Wikipedia – Hit by Pitch
- Wikipedia – Sacrifice Fly
- Wikipedia – Sacrifice Bunt
- Major League Baseball – Official Rules: 10.01 – The Rules of Scoring
- ESPN – MLB Statistics – Batting
- Baseball-reference.com – Career Leaders for OBP
- NCAA – Official Baseball Statistics Rules
- NCAA – Official Softball Statistics Rules
- NCAA – The Official NCAA Baseball and Softball Scorebook
- NFHS – Statistician’s Manual
- International Baseball Federation – Scoring Manual
Baseball Statistics Calculators
- At Bats per Home Run (ABHR)
- Batting Average (BA)
- Batting Average on Balls in Play (BABIP)
- Walks per 9 Innings (BB/9)
- Walk to Strikeout Ratio (BB/K)
- Batting Park Factor (BFP)
- Component ERA (CERA)
- Defense Independent Component ERA (DICE)
- Earned Run Average (ERA)
- Equivalent Average (EqA)
- Fielding Percentage (FCPT)
- Fielding Percentage (FIP)
- Ground Ball / Fly Ball (GB/FB)
- Ground Outs / Fly Outs (GO/AO)
- Gross Production Average (GPA)
- Hits per 9 Innings (H/9)
- Innings Pitched per Game (IP/GS)
- Isolated Power (ISO)
- Strike to Walk Ratio (K/BB)
- Left on Base Percentage (LOB%)
- On Base Percentage (OBP)
- On Base Plus Slugging (OBPS)
- Opponents Batting Average (OBA)
- Plate Appearances per Strikeout (PA/SO)
- Power Finesse Ratio (PFR)
- Pythagorean Expectation
- Run Average (RA)
- Runs Created (RC)
- Range Factor (RF)
- Runs Produced (RP)
- Stolen Base Percentage (SB%)
- Slugging Percentage (SLG)
- Save Percentage (SV%)
- Total Average (TA)
- Total Bases (TB)
- Total Chances (TC)
- Times on Base (TOB)
- Walks and Hits per Inning Pitched (WHIP)
- Extrapolated runs (XR / XRR / XRB)