What this calculator does
On-base percentage is how often a batter reaches base: hits plus walks plus hit-by-pitch, divided by at-bats plus walks plus hit-by-pitch plus sacrifice flies. It is the statistic batting average should have been.
The difference is that OBP counts walks. A player who walks 90 times has done something valuable that batting average records as nothing at all, and the gap between the two figures is largely a measure of plate discipline. Moving from 30 walks to 90 on the same hit total raises OBP from .343 to .408, which is the difference between average and excellent.
The formula
The numerator is hits plus walks plus hit-by-pitch. The denominator is at-bats plus walks plus hit-by-pitch plus sacrifice flies. Sacrifice bunts are excluded from the denominator by convention, on the basis that a bunt is a deliberate out rather than a failure to reach base. Reaching on an error does not count.
| Term | Meaning |
|---|---|
| OBP | On-base percentage, the rate of reaching base safely per plate appearance. |
| Plate appearance | Any completed turn at bat, which includes walks unlike an at-bat. |
| Sacrifice fly | Counted in the denominator; a sacrifice bunt is not. |
| OPS | On-base plus slugging, which adds OBP to slugging percentage. |
The inputs explained
| Field | What to enter |
|---|---|
| Hits | Hits. |
| Walks (BB) | Walks, including intentional walks. |
| Hit by pitch (HBP) | Times hit by a pitch. |
| At-bats | At-bats, which exclude walks and sacrifices. |
| Sacrifice flies (SF) | Sacrifice flies. Sacrifice bunts are excluded by convention and should not be entered here. |
When to use it
Evaluating a hitter properly
Batting average ignores walks entirely, so a patient hitter is systematically undervalued by it. OBP is the standard correction.
Calculating OPS
On-base plus slugging is the most common quick summary of a hitter, and OBP is half of it.
Assessing leadoff suitability
The leadoff spot is about reaching base ahead of the better hitters, which makes OBP the relevant measure rather than average or power.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much do walks raise on-base percentage?
A fixed hit total with the walk count increasing.
Questions
What is a good on-base percentage?
Around .320 is roughly league average, .360 is very good and .400 over a full season is excellent and rare. It runs 50 to 80 points above batting average for most hitters, with the gap widening for patient ones.
Why are sacrifice bunts excluded?
Because a bunt is a deliberate attempt to advance a runner rather than to reach base, so counting it as a failure to reach base would penalise a player for following instructions. Sacrifice flies are included, which is an inconsistency the rule has carried for decades.
Does reaching on an error count?
No. The batter reached base but is not credited, since the scorer has judged that a competent defensive play would have retired them. It is one of several places where OBP depends on scorer judgement.
Is OBP better than batting average?
As a measure of offensive value, clearly. It counts walks, which are worth nearly as much as singles in scoring terms and which batting average ignores entirely. Batting average persists through familiarity rather than through merit.
For power, see the slugging percentage calculator. For batting average, see the batting average calculator.