Baseball Glossary › On-Base Percentage
On-Base Percentage (OBP)
On-base percentage (OBP) measures how often a batter reaches base. It counts hits, walks and hit-by-pitches, divided by at-bats plus walks, hit-by-pitches and sacrifice flies. Reaching on an error, a fielder's choice or a dropped third strike does not count, and sacrifice bunts are left out entirely.
Formula
Worked example (illustrative numbers): a hitter has 150 hits, 60 walks and 5 hit-by-pitches in 500 at-bats, plus 5 sacrifice flies.
Times on base = 150 + 60 + 5 = 215
Denominator = 500 + 60 + 5 + 5 = 570
OBP = 215 / 570 = .377
Athletics example: Rickey Henderson
Rickey Henderson paired a .279 career batting average with a .401 on-base percentage, largely because he drew 2,190 walks. See the full career line on the Rickey Henderson player page.
OBP minus AVG = .401 - .279 = .122
That gap is the value walks and hit-by-pitches add on top of hits. Career MLB totals from our player database (MLB Stats API).
What to Know
Walks count toward OBP, and so do hit-by-pitches. That is the key difference from batting average, which ignores both. Sacrifice flies count against OBP because they are in the denominator, while sacrifice bunts are removed from the formula. Under Rule 9.21(f), times awarded first base on interference, obstruction or a shift violation are ignored.
As a rough guide, FanGraphs' rule-of-thumb chart treats about .320 as average, .340 as above average, .370 as great and .390 as excellent, while noting that league averages change from year to year. OBP is the second number in a slash line, and adding it to slugging percentage gives OPS.
MLB.com credits Dodgers executive Branch Rickey and statistician Allan Roth with developing on-base percentage, and notes it did not become an official statistic until 1984.
Frequently Asked Questions
What does OBP mean in baseball?
OBP stands for on-base percentage. It measures how often a batter reaches base through a hit, a walk or a hit-by-pitch, compared with his at-bats, walks, hit-by-pitches and sacrifice flies.
Do walks count towards on-base percentage?
Yes. Walks, including intentional walks, count as times on base in OBP. That is the main reason OBP is usually higher than batting average, which does not count walks at all.
Does a hit by pitch count for on-base percentage?
Yes. A hit-by-pitch counts as a time on base and is added to both the top and the bottom of the OBP formula. It does not count as a hit or an at-bat, so it has no effect on batting average.
Does reaching on an error count in OBP?
No. Reaching base on an error, a fielder's choice or a dropped third strike does not count as a time on base in OBP. The batter is charged with an at-bat, so those plays actually lower his on-base percentage.
How is OBP calculated?
Add hits, walks and hit-by-pitches, then divide by the sum of at-bats, walks, hit-by-pitches and sacrifice flies. For example, 215 times on base over a 570 denominator is a .377 on-base percentage.
What is a good on-base percentage?
FanGraphs' rule-of-thumb chart treats about .320 as average, .340 as above average, .370 as great and .390 as excellent. League averages shift from year to year, so compare a hitter with his own season's league.
Related Terms
Sources
- MLB.com Glossary: On-base Percentage (OBP)
- MLB.com Glossary: Sacrifice Fly (SF)
- Official Baseball Rules 2026 (MLB)
- FanGraphs Library: OBP
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