A slugging percentage of .450 or better nearly always puts a batter in the upper half of his league in terms of collecting bases, while league leaders in the 21st century typically slug around a .600 (or better clip).
Some more perspective on relative and historical slugging levels, but first …
What Is Slugging Percentage?
Slugging percentage is the total number of bases a batter gains through his at-bats in a given period, divided by his total number of at-bats over that duration.
The formula to calculate slugging percentage (or SLG) is:
SLG = [(# of singles) + 2*(# of doubles) + 3*(# of triples) + 4*(# of home runs)]/(# of at-bats)
This yields the average number of bases a batter collects per at-bat.
What Is a Good Slugging Percentage? Some Perspective
Back to our original question — what is a good slugging percentage?
Understanding the variation in that stat over time helps answer that query batter today’s batters.
For instance, the average slugging percentage over the course of baseball history has ranged from a low of .305 in 1908 to a high of .437 in 2020. If we focus on just the 21st century, through 2021, the average SLG has clocked in below .400 only twice (2013 and 2014) through 2021.
Meanwhile, the highest slugging mark in baseball has ranged from a high of .863 in 2001 (Barry Bonds) to a low of .436 in 1919 (Hi Myers). Since 2000, no player has led his league with a slugging percentage lower than .550.
So, what is a good slugging percentage?
Slug over .450, and you’re well above average.
Bump that up to .500, and you’re performing at a star level.
Add another 50 points, to .550, and you just might be a league leader.