Many of the most exciting plays in baseball are the result of big hits. A batter slicing a double into the corner, lining a triple into the alley, or crushing home runs over the wall.
These are the types of plays that get fans out of their seats and on their feet and these plays are reflected in one popular stat that emphasizes swinging for the fences: slugging percentage.
So what is slugging percentage?
Slugging percentage is a statistic that measures how proficient a batter is at hitting so-called extra-base hits: doubles, triples, and home runs. A player’s slugging percentage represents the number of bases they earn per at bat. The stat is calculated by taking total bases and dividing by at bats.
However, because of all the factors that go into slugging percentage, there isn’t necessarily a correlation between how good of a power hitter someone is and how good of a slugging percentage they have.
Let’s look further into the statistic:
What Is Slugging Percentage in Baseball?
With slugging percentage, the goal of the statistic is to assign a number to show how effective a hitter is at driving the ball and racking up extra-base hits.
While the name of the stat is “slugging percentage,” the name itself is slightly inaccurate, as it is a ratio, or a so-called “rate stat,” rather than a true percentage.
A batter’s slugging percentage (often abbreviated as SLUG or SLG, or just referred to as “slugging,”) is the total number of bases or the number of bases he earns in all of his hits divided by the total number of his official at bats and presented in the form of a decimal rounded to three places.
What the statistic boils down to is determining the average number of bases that a batter would gain for every official at bat, meaning that both the skill to collect extra-base hits and the ability to do so rather often both are key factors in a high slugging percentage.
Now we’ll dive into how you figure out what that number is.
How Do You Calculate Slugging Percentage in Baseball?
To calculate slugging percentage for a player, you will need two pieces of information: the total number of at bats and the total number of bases he accumulates.
The slugging percentage formula is rather simple, as it’s calculated by dividing the total number of bases by the total number of at bats. To calculate total bases, you take a batter’s total number of hits and add one additional base for each double, two for each triple, and three for each homer.
Written out, the equation reads as this: [1B + (2B x 2) + (3B x 3) + (HRx4)]/AB.
One key thing to note when calculating slugging percentage is that it only takes into account official at bats. As defined by Major League Baseball, an at bat is granted when a hitter gets a hit, reaches via fielder’s choice or error, or is put out on a non-sacrifice.
For the sake of at bats, bases on balls (walks), hit-by-pitch, sacrifice bunts, and sacrifice flies are all omitted from the at bat ledger, with those numbers being lumped into the “plate appearances” ledger.
For practice, let’s calculate the slugging percentage of a hitter:
Let’s say that a batter has 235 plate appearances, but has walked 20 times and has been hit by five pitches, laid down five sacrifice bunts, and hit five sacrifice flies. Those last four columns (20+5+5+5) will all be omitted, so the number of at bats for the batter is 200.
We’ll say that he collected 60 hits in those 200 at bats, with ten doubles, five triples, and ten home runs.
To find total bases, you start with the 60 hits, add 10 for doubles (one base for each), another 10 for triples (two bases each), and 30 for home runs (three bases each). With the added bases, 10+10+30=50, so add 50 to the 60 hits and you get 110 total bases.
Finally, you divide 110 total bases by 200 at bats and you come up with a slugging percentage of 0.55. That number is almost always written as three decimals, so it will be written as .550, meaning that our example batter will record, on average .55 total bases per at bat. The question is, is that a good number or not?
What Is a Good Slugging Percentage in Baseball?
Because slugging percentage is a rate stat, in Major League Baseball it is subject to up-and-down fluctuations as league conditions change.
These changes could be a different composition of the actual baseball, rule changes, new ballparks (different dimensions) or even changing trends in pitcher usage or weather that is poorer than normal throughout a season.
Despite this, there is more or less a defined benchmark for a “good” slugging percentage. A .450 slugging percentage is considered good and a .550 slugging percentage is outstanding. Likewise, moving towards the extremes, a .350 slugging percentage is poor and a .650 slugging percentage is elite.
For some context, since 2005, every American and National League leader in slugging percentage has fallen between .551 and .671. On the other side of the spectrum, 119 batters since 2005 have posted a slugging percentage below .350 in that timespan.
However, this illustrates the number of factors that go into a player’s slugging percentage.
For example, eight players since 2005 have topped a .650 slugging average in a season. Among these eight players, all of them batted over .300, and all of them recorded at least 37 home runs, showing an elite combination of hitting for power and hitting for a high average.
On the other side, of the 119 men below .350 in a season, only one of them, Luis Castillo, hit over .300, batting .302 in 2009, thanks to the fact that he recorded only 16 extra-base hits for the entire season.
Because four singles account for as many total bases as one home run, an effective singles hitter can still post a respectable batting average despite a low slugging percentage.
Also on that list, only 15 of the 119 players hit ten or more home runs that season, with no one hitting more than 16 home runs.
Among that group, none posted a batting average higher than .252, a rather mediocre number that illustrates that hitting for a little more power while sacrificing your batting average can have detrimental effects on your overall numbers.
History of Slugging Percentage
Slugging percentage is a relatively new statistic compared to many of the traditional numbers, but it has nonetheless been in common use for several decades.
A precursor to slugging percentage, “total bases average,” was invented by Henry Chadwick in 1867, listing a player’s total bases per game. The modern slugging percentage, using total bases per at bat, not per game, became an official National League statistic in 1923, and American League in 1946.
Chadwick, a baseball statistics and sports writing pioneer, was decades ahead of his time in his belief that hits alone did not tell the full story of a batter’s effectiveness, and also cited the fact that many hits in those days were compounded by errors, as fielders did not wear gloves.
Thus a batter might only collect a single, but reach third base thanks to an error on the play, Chadwick’s system only gave the batter credit for the one base.
Popular usage would be decades away, as one of the first documented mainstream usages of slugging percentage was on the back of Ralph Kiner’s 1952 Bowman baseball card, which noted that he was the National League leader in slugging percentage the year prior, though it wasn’t until 1981 that slugging percentage regularly appeared on the back of baseball cards.
With slugging percentage now a common term in the baseball lexicon, you’ll have a better idea when you see it on a player’s stat line whether he’s a slap hitter or a feared slugger.
Career Slugging Percentage Leaders
Here are the top 5 in terms of career slugging percentage:
- Babe Ruth – .6897 career slugging percentage
- Ted Williams – .6338 career slugging percentage
- Lou Gehrig – .6324 career slugging percentage
- Jimmie Foxx – .6093 career slugging percentage
- Barry Bonds – .6069 career slugging percentage
- Hank Greenberg – .6050 career slugging percentage
- Mark McGwire – .5882 career slugging percentage
- Manny Ramirez – .5854 career slugging percentage
- Mike Trout – .5821 career slugging percentage
- Joe DiMaggio – .5788 slugging percentage
What Is On Base Percentage?
On base percentage (OBP) is a measure of how often a batter reaches base per plate appearance. On base percentage includes walks, hits, and hit-by pitches, but doesn’t factor in errors, fielder’s choice, dropped strike three, fielder’s obstruction, catcher’s interference, and sacrifice bunts.
Odds and Ends About Slugging Percentage
- The highest single-season slugging percentage is .863, set by Barry Bonds in 2001. Bonds compiled 411 total bases in just 476 at bats that season, which included a Major League record 73 home runs. His batting average was also .328 for the season.
- Bonds’ single-season record broke an 81-year-old mark of .847 set by Babe Ruth in 1920. The top six marks for slugging percentage in a season are held by Bonds and Ruth, with each man claiming three of those historic seasons. They are also the only players in MLB history to record a slugging percentage over .800 in a single season, with each of them doing so twice.
- The highest single-season slugging percentage for a team in history is .495, set by the 2019 Houston Astros, who collectively hit 288 home runs. The 2019 Minnesota Twins and 2019 New York Yankees also posted .494 and .490 marks, respectively, the second and fourth-highest marks in MLB history. The Astros had the highest batting average of the three teams, hitting .274.