What is the name of the baseball statistic that measures a batter's ability to get on base?

The baseball statistic that measures a batter’s ability to get on base is on-base percentage, commonly abbreviated OBP. It estimates how frequently a hitter reaches base through a hit, walk, or hit by pitch.

The standard formula is (hits + walks + hit by pitch) divided by (at-bats + walks + hit by pitch + sacrifice flies). Unlike batting average, OBP gives credit for walks and being hit by a pitch, because both events help a batter become a potential run scorer. Reaching on an error or fielder’s choice generally does not count as reaching base for OBP.

The statistic was developed in the late 1940s by Brooklyn Dodgers statistician Allan Roth in collaboration with general manager Branch Rickey. It became an official MLB statistic in 1984 and gained wider public attention after the 2003 book Moneyball emphasized undervalued on-base skills.

OBP is often confused with OPS. OPS combines on-base percentage with slugging percentage, adding a measure of power to a measure of reaching base. Batting average, by contrast, counts hits divided by at-bats and ignores walks entirely.