Batting average on balls in play

Batting average on balls in play is a measure of the number of batted balls that safely fall in for a hit not including home runs.

BABIP = (H-HR) / (AB-K-HR+SF)

where H is hits, HR is home runs, AB is at bats, K is strikeouts, and SF is sacrifice flies.

There are many factors that affect BABIP, including batted ball types, ballparks, team defense, foot speed, luck or randomness. As with any stat, sample size is also an important consideration here. However, both for batters and pitchers, it tends to congregate around the league average and large variations are almost never repeared year-to-year, which tends to demonstrate that they are simply based on luck. One demonstrated difference is that knuckleball pitchers tend to have a lower BABIP than other pitchers, as the tricky pitch does in fact induce a higher rate of weak contact.

Further Reading

• Steve Gardner: "MLB advanced statistics: Your guide to WAR, BABIP, FIP and more", USA Today, July 17, 2019. [1]