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A complete beginner’s guide to baseball stats: Batting statistics, and what they mean

If you have ever wondered what all those numbers we use in our articles mean, we have you covered.

Detroit Tigers v Milwaukee Brewers Photo by Dylan Buell/Getty Images

Baseball is a numbers game.

All sports have statistics, but there is something about baseball that lends itself to being the perfect sport for number nerds everywhere. So much so there’s even a specific name given to the study of baseball statistics: sabermetrics.

With all those crazy things like DRS and wRC+ being thrown around in baseball articles, it can be difficult for baseball writers to remember that there are those who don’t obsess over the minutiae of the game, but just enjoy it for what it is: a game. With that said, in order to make life easier for those who don’t know much about baseball statistics, we’re going to do a deep dive on what different baseball stats mean. Starting with this overview, which is basically how to understand a box score, we’ll also delve into pitching basics tomorrow, and then get into more advanced stats.

Consider this a 101 course in baseball statistics. By the time the 2019 season begins, you should have a good grasp on what different numbers mean, how they’re calculated, and what the heck we’re talking about when we mention UZR.

Without further ado, let’s break down the basics of a box score.

Here’s the Tigers box score from a July 10 game versus the Tampa Bay Rays. We have excluded the pitching stats, which will be featured in the next post.

Courtesy of ESPN

At Bats (AB)

This one is pretty self explanatory, but can be somewhat confusing. At Bats, represented as AB in a box score, indicate how many times an individual player came up to the plate, and had one of the following things happen: a hit, a strikeout, reaching on an error, fielder’s choice.

What doesn’t count as an at bat: a walk, a sacrifice play, a hit by pitch. Hence some of the disparity in the numbers above, with Jose Iglesias appearing to have fewer at bats than the others in the lineup, but he also has a walk.

Similar to at bats is plate appearances, represented as PA in a stat. Plate appearances are a more literal indication of how many times a player actually appeared at the plate, because it encompasses both of the lists above.

It’s important to note that if catcher interference occurs in a play, then 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 work of another batter. A run batted in (RBI) indicates the a run scored as a result of the hitter’s efforts. Confused? No problem.

In the box score above, we see that Jeimer Candelario has a run, but not an RBI. This means that while he did cross home plate and score a run, it wasn’t as a result of his own at bat. Both Nicholas Castellanos and Niko Goodrum have RBIs. Without checking the play-by-play, this leads me to believe that Castellanos had a hit which scored Candelario, and Goodrum had a hit that scored Castellanos. Let’s see.

Courtesy of ESPN

Ding ding ding. How did I figure that out without looking? Because both Candelario and Castellanos had runs, but only Castellanos and Goodrum have RBIs. Based on the batting order, and the limited number of runs and RBIs in the game, the above conclusion was easier to reach. This obviously gets quite a bit harder in games where there are more runs and RBIs, but this is a good way to get a handle on the difference between the two stats.

Hits (H)

A hit (H) is when the batter reaches at least first base in their at bat. This gets slightly more involved, because a batter can reach first on an error or fielder’s choice, and this does not count as a hit.

**A note here, because I keep using the terms and don’t want to add confusion. An error is considered any event where the fielder misplayed the ball in such a manner as to allow the batter to reach base. An error that results in a batter reaching base won’t count as a hit, but will count as an at bat. A fielder’s choice indicates that an offensive player allowed the batter to reach first base as a result of attempting to put out a different runner in play. For example if a short stop decided to try to throw out a runner advancing on third instead of throwing out the batter heading to first base, this would be considered a fielder’s choice**

Back to the hit. A hit excludes an error or fielder’s choice, so it is possible for a batter to reach first and not have it count as a hit.

The hit stat is further broken out into notations that indicate just how far the batter got. 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.

Base on Balls (BB)

This stat is a fancy way of saying walks. This solely reflects when a batter sees four balls and is rewarded first base as a result. An intentional walk (sometimes represented as IBB, or intentional base on balls) also counts as a walk. What does not count as a walk is when a batter is hit by the ball (hit by pitch or HBP) and is rewarded a tripe to first base as a result.

Strikeouts (K)

Strikeouts are pretty straightforward, a strikeout represents a batter seeing or swinging at three strikes, and therefore ending their at bat. In a game, this can be denoted by a K which represents a swinging strikeout, or a which indicates a strikeout looking, where the batter did not take a swing at the final strike of the at bat.

Batting Stats

The next part of understanding baseball stats are the three main batting stats: batting average (BA, or AVG above), on-base percentage (OBP), and slugging (SLG). You will often see these represented as three stats side by side, separated by slashes, which has lead to the nickname of a “slash line,” like .220/.267/.314 (James McCann’s 2018 slash line). If ever you read that a player “slashed” a certain number, this will usually be followed by the above three statistics. A fourth batting stat of on-base plus slugging (OPS) is exactly what it sounds like, a combination of on-base percentage and slugging percentage.

Let’s see how each of those numbers are calculated.

Batting Average (AVG or BA)

This one is pretty easy. Batting average (BA) is calculated by taking a player’s total hits and dividing them by at bats. The above box score would represent a player’s season total batting average, rather than just a single game average. This gives a more complete representation of how a player is doing to date.

A .300 average would indicate that a player collected a hit on three of every 10 at bats. Ted Williams, Hall of Famer, two-time Triple Crown winner, and generally considered to be one of the best hitters in history (.344 career BA), once said, “A .300 hitter, that rarest of breeds these days, goes through life with the certainty that he will fail at his job seven out of ten times.”

On-base percentage (OBP)

This can also occasionally be referred to as on-base average (OBA). If you’ve watched Moneyball you might have a vague understanding of why this stat is coveted by some clubs as being more valuable that batting average. This stat encompasses more than just batting average in that it takes into account all times a hitter reaches base.

Errors and fielder’s choice once again ton’t count towards this total, but it does include hits, walks, and a batter being hit by pitch. Some like this stat more 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.

In mathematical terms, on-base percentage is calculated by taking the total number of hits, walks, and hit by pitch, and dividing it by the total number of at bats, walks, hit by pitch, and sacrifice flies. Yeah that’s a lot. No wonder it’s considered to be more inclusive.

Slugging (SLG)

Okay, we’re going to get really mathy here, so bear with me. Slugging encompasses total bases (including all extra base hits) divided by at bats. The easiest way to understand this is to see the formula.

Courtesy of Wikipedia

Who else feels like you’re back in a high school math class? The benefit of slugging as a stat is that it adds additional weight to a player’s extra base hits, rather than rating all hits the same, as batting average does. This gives a batter with a propensity for more triples and home runs a higher overall slugging percentage than a batter who almost solely hits singles and doubles. It allows for a better overall picture of a player’s production at the plate.

On-base plus slugging (OPS)

This can be considered an overall assessment of a player’s production, as it considers both 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. For the Tigers, their OPS leader last season was Nicholas Castellanos, who had an OBP of .354, a SLG of .500 and an OPS of .854.

To get just slightly more advanced, you might also see OPS+ listed next to OPS. OPS+ takes a player’s OPS and then adjusts for external factors, like which parks were played in (as some are more hitter friendly than others). OPS+ then is converted onto a scale, where 100 is considered the league average, and the number following it indicates the percentage better than average a player is. For example, Castellanos has an OPS+ of 130 in 2018, indicating his was 30 percent better than league average.

This number is reached by dividing OPS by league OPS, which has been adjusted by park factors, and multiplied by 100.

OPS+ starts to get us a little more into advanced stats, so we’ll wrap up our basic stat lesson here. Stay tuned for pitching basics tomorrow, if you ever wondered about ERA, WHIP, and FIP.