Baseball On-Base Percentage (OBP)

Since players must sequentially touch all four bases in baseball to score, a player’s ability to get on base is an important factor to measure. On-Base Percentage, otherwise known by the abbreviation OBP, measures the frequency of a batter reaching base. Read on to learn more about On-Base Percentage and how it’s calculated.

On-Base Percentage (OBP)

On-base percentage (abbreviated as OBP) measures the frequency that a batter reaches base. It is calculated by dividing the number of times the batter reaches base, by their number of plate appearances (Times on Base/Plate Appearances). Like batting average, on-base percentage is expressed as a decimal to the thousandths place.

Since on-base percentage incorporates walks as well as hits, a player's OBP is usually higher than his batting average. An average OBP is around .320, and what would typically be considered a good OBP is around .370 or over.

OBP Formula

The more complete version of the formula includes what exactly is considered a Time on Base or a Plate Appearance. Here is the detailed formula:

(Hits + Walks + Hit-by-pitch) / (At-bats + Walks + Hit-by-pitch + Sacrifice flies) = OBP

Example

If a player goes to bat three times in a game and gets two hits, one walk, one sacrifice fly and no hit by pitch, their OBP for the game  is .600. This is because (2 + 1 + 0) / (3 + 1 + 0 + 1) = 3 / 5 = .600. That means that the player reaches base about 60% of the time in that single game.

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