what is slg in baseball

What is Slugging Percentage (SLG) in Baseball?

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Baseball fans around the world are starting to see that the game they have grown to love over the years is changing slightly. A game that was once driven by what happened on the field is slowly but surely starting to become more statistics-driven.

While some may view this as a negative change to the game, those that understand the numbers that are driving the decisions made by scouts, executives, and managers can see that the statistics can actually make the game more intriguing.

Gone are the days where a hitter’s productivity was based on his batting average and home run as are the days where pitchers were evaluated based on wins and ERA. Baseball statistics have never been more complex, and understanding what those stats mean is key to understanding today’s game.

One of the most misunderstood statistics in baseball is slugging percentage.

Slugging percentage is a statistic used to measure the power productivity of a hitter. It is calculated by adding up the hitter’s total bases and dividing that number by the hitter’s total at-bats. Slugging percentage gives more weight to extra base hits than batting average where all hits are equal.

An Example on How to Calculate Slugging Percentage (SLG)

Here is an example using two made-up players: Player A and Player B.

Player A1003225511.320 
Player B1002510807.250 

To make things easy, we will say both players have exactly 100 at-bats (AB). As you can see, Player A has more hits (H) than Player B making his batting average (BA) higher.

When calculating their slugging percentage, we will use this formula:

1B(1) + 2B(2) + 3B(3) + HR(4) / AB = SLG.

In this formula, the numerator is the total number of bases, so all singles are multiplied by one. Doubles are multiplied by two, triples by three, and home runs by four.

Here is how to calculate Player A’s slugging percentage:

25(1) + 5(2) + 1(3) + 1(4) / 100 = SLG.

25 + 10 + 3 + 4 / 100 = SLG.

42 / 100 = .420

Now let’s calculate Player B’s slugging percentage:

10(1) + 8(2) + 0(3) + 7(4) / 100 = SLG.

10 + 16 + 0 + 28 / 100 = SLG.

54 / 100 = .540

Here is a comparison again in a table format, this time with the slugging percentage included:

Player A1003225511.320.420
Player B1002510807.250.540

Player A has a higher batting average than Player B because he has more hits. Remember, batting average counts all hits as equal. But because Player B has more extra base hits, especially more home runs, than Player A, his slugging percentage is higher.

This does not necessarily mean that Player B is a better hitter than Player A, but it does mean that he has more power productivity. While Player A may get more hits, Player B has a chance to do more damage at the plate.

Watch this video for a more in-depth but easy to follow explanation on how to calculate slugging percentage.

The History of Slugging Percentage

While it took some time for slugging percentage to gain popularity in baseball, the statistic has been around since the early 1950s.

Not only is former Los Angeles Dodgers executive Branch Rickey credited with helping break Major League Baseball’s color barrier by signing Jackie Robinson, he is also responsible for creating the formula to determine a hitter’s slugging percentage.

But Rickey can’t be solely credited with the invention of this statistic. It turns out, he was way ahead of his time in all aspects of the game as he was the first to hire baseball’s first full-time statistician, Allan Roth, in 1947.

Together, Roth and Rickey tabbed what they called at the time “Extra Base Power” (EBP) as a better way to evaluate a hitter’s productivity. Rickey made the statistic known to the public when he referenced it in an article written in Time Magazine.

This formula would later come to be known as slugging percentage and gained popularity thanks to Bill James’ SABRmetrics in which he used it to develop his own formula called “Runs Created” (explained later).

How Slugging Percentage is Used to Make Decisions

There are many ways that slugging percentage can be used to help coaches, scouts, and executives make decisions — whether they be personnel or in-game decisions — to help put the best baseball team on the field.

As stated in the video in the “ Example” section above, slugging percentage can be used by coaches to determine how to structure the batting lineup. The players with the highest slugging percentage should be placed in the spots in the lineup in which the coach wants his biggest power threats.

This strategy can be used by managers and coaches at all levels because it does not require a lot of in-depth analysis.

A more complex use of slugging percentage is to calculate a player’s OPS (on-base plus slugging percentage). This statistic is the sum of two valuable statistics and can be used to evaluate a player’s power productivity along with how often that player reaches base.

Let’s go back to Players A and B to calculate their OPS.

Player A11510032105.320.408.420.828
Player B11510025132.250.347.540.887

Here, we just simply added Player A’s OBP and SLG (.408 + .420) and did the same with Player B (.347 +.540) to get their OPS. As you can see, Player B is still a little more valuable in terms of getting on-base and exhibiting power than Player A according to their OPS.

(For more information about on-base percentage, check out the article “What is a Good On-Base Percentage in Baseball”)

Scouts and executives at the professional level may use this statistic to evaluate a player’s potential impact on their team. This helps them sift through players who give them the most bang for their buck.

Another even more advanced use of slugging percentage is often used by professional teams when making personnel decisions: Bill James’s Runs Created formula (referenced earlier).

Teams that are analytics-driven use this to determine how many runs they believe a player will generate for their team in a given season. The formula looks like this:

[(Hits + Walks+HBP)(Total Bases)] / [At Bats + Walks+HBP] = Runs Created

For fun, let’s calculate Player A and B’s Runs Created as well.

Player A1151003210542.320.408.420.828
Player B1151002513254.250.347.540.887

Player A:

[(32 + 10 + 5)(42)] / [100+10+5] = RC

[(47)(42)] / [115] = RC

[1,974] / [115] = 17.16

Player B:

[(25 + 13 + 2)(54)] / [100+13+2] = RC

[(40)(42)] / [115] = RC

[1,680] / [115] = 14.61

This shows how much more complex analytics can be and shows that SABR metrics driven teams would likely value Player A over Player B.

However it is used, slugging percentage has made its case as a statistic that is more valuable than batting average to people in charge of making in-game and personnel decisions.

Slugging Percentage Records

Photo by Dennis Sylvester Hurd

Here are the top five career slugging percentage leaders in Major League Baseball history:

  1. Babe Ruth – .689
  2. Ted Williams – .633
  3. Lou Gehrig – .632
  4. Mule Suttles – .617
  5. Turkey Stearnes – .616

Here are the top five single season slugging percentage leaders in Major League Baseball history:

  1. Josh Gibson – .974 (1937)
  2. Mule Suttles – .877 (1926)
  3. Charlie Smith – .869 (1929)
  4. Josh Gibson – .867 (1943)
  5. Barry Bonds – .863 (2001)

As can be seen by this list, many of these players accomplished these feats in years where slugging percentage was not even calculated. Thankfully, baseball historians have gone back and given them the credit they deserve.

In the last thirty years in the MLB, there have only been four seasons where the league’s slugging percentage as a whole was below .400. This season’s slugging percentage is currently .402 which is down from 2019, the last full Major League season, in which the slugging percentage was .435.

This decrease proves that power numbers across the league are down. This may be due to pitchers becoming more dominant in recent years. After all, this year’s season is far from over, so there is still time for that slugging percentage to rise.

Frequently Asked Questions

Why aren’t walks and hit-by-pitches calculated into slugging percentage?

The slugging percentage is designed to reflect the hitter’s power productivity when he puts the ball in play. While walks and hit-by-pitches are valuable statistics, they do not show a player’s power potential. This is why OPS was created.

Do professional scouts use slugging percentage in drafting players?

When it comes to drafting college players, it is likely that scouts will look at a player’s slugging percentage as a piece to the puzzle when deciding if he is worthy of being drafted. When it comes to drafting high school players, high school statistics are less reliable, so it is likely not considered as much.

Is it possible for a slugging percentage to be over 1.000?

Yes, it is possible for a player to slug over 1.000. In order to do this, most of a player’s hits would have to be extra base hits.

What is a perfect slugging percentage?

A perfect slugging percentage is 4.000. In order to accomplish this, a player must never make an out and only hit home runs. This is virtually impossible over the length of a season.

See Also:
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How Long Does a High School Baseball Season Last?
What is a Walk Off Home Run? (Explained)