Baseball 101: Beginner batting stats

Welcome back to our new offseason series “Baseball 101.” If you missed the first post, where we explained the positions and basic lineup construction, you can find that here. As with the previous entry, I’ll also be including a video-format version at the bottom to help those who would prefer to watch/listen rather than read.

In this entry we’ll be discussing some very basic batting terminology: hits, walks, batting average, and the most common terms we see used in regular articles as well as during games. Next week we’ll be posting a similar explainer for pitching terminology.

At Bats (AB) and Plate Appearances (PA)

While you might think this is easy, let’s not get too ahead of ourselves. An “at bat” and a “plate appearance” are NOT actually the same thing. At Bats, written as AB in a box score or stat line, indicate how many times a player came up to the plate, and achieved one of the following results: a hit, a strikeout, reaching on an error, or a fielder’s choice.

What does NOT count as an at bat are the following: a walk, a sacrifice play, or a hit by pitch. Because of this differentiation, a player’s stat line will show a difference between at bats and plate appearances.

So what is a plate appearance?

Represented as PA in a stat line (and rarely used in a single game box score), plate appearances are a bit more literal in that they represent how many times a player actually stepped up to the plate. Any or all of the above results would still count as a plate appearance, with one VERY unique exception: if catcher interference occurs in a play, the trip to the plate is not counted as either an at bat or a plate appearance.

Run (R) and Runs Batted In (RBI)

A run (R) is counted when the batter reaches home plate, either by their own work (a home run) or by the efforts of another batter. A run batted in (RBI) indicates a run scored as a result of the hitter’s efforts.

Wait, what?

Basically, a player can have a run in their stat column without having hit the ball that scored that run. Say, for example, Kevin Kiermaier hits a double, and shortly after that Manuel Margot hits a home run. Kiermaier will be credited with a run for crossing home plate, while Margot will be credited with a run (he crossed home plate himself) and TWO RBIs because his home run was what BATTED IN both Kiermaier and himself.

Hits (H)

A hit (H) is when the batter reaches first base (or beyond) as a result of their at bat. However, there are ways a batter can reach first base that do NOT count as a hit. For example, if a batter reaches first on an error* or fielder’s choice, and this would not be considered a hit.

*Ashley, you keep talking about errors and I have no idea what those are. No problem, bestie. An error is considered any event where the fielder misplayed the ball in such a manner as to allow the batter to reach base when they likely would not have otherwise. An error that results in a batter reaching base won’t count as a hit, but will count as an at bat.

The hit stat is taken a step further to indicate how far the batter got on the basepaths. A double, where the batter reaches second base, is represented by 2B. A triple, where the batter reaches third base, is represented by a 3B. A home run is represented by an HR. These are all classified as “extra-base hits.” Most basic game box scores just list hits, but a player’s stat page on a site like Baseball Reference or FanGraphs will give a more detailed breakdown that also includes doubles, triples, and home runs.

Base on Balls (BB) aka Walks

This indicates when a batter sees four balls and gets to advance first base as a result. An intentional walk (sometimes represented as IBB, or intentional base on balls) also counts as a walk. A player can also advance to first if they are hit by the ball (this is called a hit by pitch and shown as HBP), but this does not count as a walk or a hit.

Strikeouts (K)

Strikeouts are pretty straightforward, a strikeout is when a batter sees or swings at three strikes, and therefore ends their at bat. In a game, this can be denoted by a K which represents a swinging strikeout, or a ꓘ which indicates a strikeout looking, where the batter did not take a swing at the final strike of the at bat. Now you know what that big wall of Ks is at most ballparks (and in the case of Tropicana Field, you’ll know whether or not you get free tacos.)

Batting Stats

Let’s get a little more advanced now, and learn about the most basic four batting statistics: batting average (BA, usually, or occasionally AVG), on-base percentage (OBP), and slugging (SLG). In articles, you will often see these three stats side by side, separated by slashes, which is colloquially known as a “slash line.” If you’ve read any article about a player’s performance, you’ll definitely have noticed a slash line, they look like this: .229/.348/.411 (Ji-Man Choi’s line from 2021). We’ll break down those three stats as well as one more: on-base plus slugging (OPS), which is exactly what it sounds like, a combination of on-base percentage and slugging percentage.

Let’s see what we mean by each of the stats above.

Batting Average (AVG or BA)

The most basic of basic stats, this is the one you will normally see mentioned during a game in the little box below a player’s name. Batting average (BA) is calculated by taking a player’s total hits and dividing them by the number of at bats.

For example, a .300 average would indicate that a player collected a hit three out of every 10 at bats. This may seem low, but a .300 average for a season is exceptionally rare. In 2021 only 14 players ended the season with a batting average over .300, and the highest was Trea Turner at .328.

On-base percentage (OBP)

This stat takes into account all times a hitter reaches base, which means it offers a slightly more well-rounded summary of a player’s successes and achievements (this is by no means the most complete stat, and we’ll discuss some better and more frequently used ones, like wRC+ in later installments), so just know that while this is a useful stat, it’s not frequently discussed outside a slash line.

Excluding errors and fielder’s choice, this stat DOES include hits, walks, and hit by pitch, basically any event that would see a batter getting on base and converting themselves into a baserunner. It’s a more inclusive stat than batting average because it represents a more complete picture of the batter’s success at plate, because a walk is just a good as a hit in terms of putting a batter in position to score.

If you want to understand the math of how this number is reached, you would take the total number of hits, walks, and hits by pitch, then divide that by the total number of at bats, walks, hits by pitch, and sacrifice flies. This is why we don’t recommend you try to do the math yourself.

Slugging (SLG)

Here’s where things get super ugly in terms of math, so we won’t be explaining the breakdowns quite so precisely from this point forward. Basically, slugging encompasses total bases (including all extra base hits) divided by at bats.

The benefit of this is that extra-base hits are weighted differently than a walk or a single base hit. SLG is BA if batting average gave higher grades for doubles or triples. If we see that a player has a high SLG, this indicates they hit more extra-base hits than someone who is just good at getting single-base hits. It allows for a better overall picture of a player’s production at the plate.

Again, like OBP this isn’t a stat we generally see used on its own the same way batting average is, but by being able to recognize what it means, we can better understand what a player is bringing to the table.

On-base plus slugging (OPS)

While this stat is not so frequently used, it does come up especially on Baseball Reference, and is a very, very early precursor to some of the much more advanced stats we’ll discuss later on. OPS (or it’s easier to understand sister OPS+) gives us a better overall assessment of a player’s production, because it combines OBP and Slugging, the two more involved stats we looked at above.

What does that mean?

OPS looks at how often the batter gets to base (OBP) and how often they are hitting for extra bases (SLG). If ever you see someone hitting with a OPS over 1.000 you can generally understand that they are having an absolutely incredible season at the plate. In 2021 only two players had an OPS over 1.000: Vlad Guerrero Jr. and Bryce Harper. This goes to show how difficult it is to excel at both getting on base and getting FAR onto base.

So what is this mysterious OPS+ I mentioned and why is it easier to understand? OPS+ takes a player’s OPS and then adjusts for external factors, like which parks were played in (some parks are considered to be more hitter friendly than others). OPS+ is then shown on a 100 scale which is where the ease of understanding comes into play. Any statistic with a + symbol in it is written out in a 100-scale format, where 100 is considered the league average. Any number OVER 100 is the percentage better than league average that player is, or under, if they are below 100.

I doubt you want the math, but if you’re curious, this number is calculated by dividing OPS by league OPS, which has been adjusted by park factors (don’t ask me how those are calculated, please), and multiplied by 100.

In current baseball writing, OPS+ is most commonly used by those who favor Baseball Reference for their statistics, whereas the more inclusive stat of wRC+ is favored by FanGraphs. The two are somewhat similar in what they try to represent, but should not be used interchangeably.

When we get into more advanced batting stats in a couple of weeks I’ll do a better job explaining wRC+ and its friend wOBA.

If video is more your speed, here’s one on Strikes, Hits and Walks:

And here’s one about the basic batting stats:

If there are topics you’d like to see covered, please comment down below, we got some great suggestions in the last post and will continue to add to our list as the weeks continue.