BABIP = (H − HR) / (AB − K − HR + SF). It strips out home runs and strikeouts to measure how often batted balls become hits.
MLB league-average BABIP hovers around .295–.305. A hitter above .350 has likely gotten lucky on placement; below .250 suggests bad luck.
Caveats: speedy hitters (more infield hits) and elite Hard-Hit% bats systematically run higher BABIPs, so it isn't pure luck for them.
BABIP closely tracks AVG, so early-season outliers in batting average usually correct as BABIP normalizes. Pitchers use opponent BABIP the same way to filter out unlucky runs.
→ Related: AVG / Hard-Hit / xBA & xSLG