Baseball Statistics Glossary

Jun 12, 2016; Pittsburgh, PA, USA; A major league baseball rest in the grass prior to the game between the Pittsburgh Pirates and the St. Louis Cardinals at PNC Park. Mandatory Credit: Charles LeClaire-USA TODAY Sports
Jun 12, 2016; Pittsburgh, PA, USA; A major league baseball rest in the grass prior to the game between the Pittsburgh Pirates and the St. Louis Cardinals at PNC Park. Mandatory Credit: Charles LeClaire-USA TODAY Sports /
1 of 3


Ever watched an MLB game and wondered, “What does that stat mean?!” We’ve put together a list for you and yours to refer to when you have those moments!

This listing will not be a comprehensive list of all MLB statistics, as that would be a 300-400 page book to read just to explain all the statistical terms you see in major league baseball and fantasy baseball, let alone when you start adding in more modern sabermetric terms.

We’ll take some of the most common terms that you will want to know to understand and enjoy the game and break them down with a basic definition that allows you to understand and/or explain the term to friends and family who may be confused. We will also divide this up into three sections – hitting/offense, pitching, and fielding/defense. Let’s start with hitting.


Basic Terms and Information

  • At Bat (AB) – A plate appearance that doesn’t end in a sacrifice, walk, or hit by pitch.
  • Batting Average (BA or AVG) – Hits divided by at bats.
  • Double (2B) – A two-base hit. Commonly nicknamed a two-bagger.
  • Hit (H) – A ball put in play in fair territory with no out recorded that a fielder would not have “normally” have been expected to catch.
  • Home Run (HR) – A four-base hit. Lots of nicknames for the home run, including homer, tater, round tripper, bomb, and many others.
  • Plate Appearance (PA) – Any time a player completes a time to the plate. Used in certain percentage calculations.
  • Run (R) – When a player scores a run.
  • Runs Batted In (RBI) – When a batter does something that causes a run to score, other than by error, he is awarded a run batted in.
  • Stolen Base (SB) – When a runner goes from one base to another during a pitch.
  • Triple (3B) – A three-base hit. Commonly nicknamed a three-bagger.

More Advanced Stuff

  • Batting Average On Balls In Play (BABIP) – The batting average that a batter has when he puts the ball into play. League average is typically around .300. Batters can typically “control” theirs with their batting style. Drastic above normal numbers or below normal numbers can indicate a regression to the mean coming in following season(s).
  • On Base Percentage (OBP) – The times a batter has been on base, calculated by walks plus hits plus hit-by-pitch, then dividing that by at bats plus walks plus hit-by-pitch plus sacrifice flies.
  • On Base Plus Slugging (OPS) – A combination measure of adding on base percentage and slugging percentage together as a measure of total offensive contribution.
  • Slugging Percentage (SLG) – A measure of the amount of bases that each hit a player gets. Rather than using hits like batting average, it takes total bases divided by at bats.

A Few Sabermetric Terms To Know

  • Exit Velocity – Similar to launch angle, this is information that became public after the 2015 season for the first time. It is the measure of the speed of the ball leaving the bat after contact. Higher velocities are better, but it’s combined with launch angle that they find the best exit velocity for home runs in combination with the ideal launch angle is 100-110 MPH.
  • Launch Angle – The angle that a ball leaves the bat. Too shallow, and the ball is always a ground ball. Too high, and it’s a pop up. Per research from 2015 data, the best angle for a home run is roughly 20-30 degrees, though on average, Kris Bryant led the majors last year with just over a 19-degree average launch angle.
  • On Base Plus Slugging Plus(OPS+) – A weighted statistic for OPS by comparing the OPS of every hitter in a particular stadium and how an individual hitter performs in comparison. The score is 100 for exactly league average, and above 100 indicates better than league average, below 100 indicates worse than league average.
  • Runs Created (RC) – A statistic to estimate the number of runs that a hitter contributes to his team. There are multiple ways to compute this, much like wins above replacement (WAR), so watch the scoring, but the original formula from Bill James was walks plus hits, then taking that number times total bases, then dividing that amount by the sum of at bats plus walks.
  • Weighted Runs Created (wRC) – Statistic utilizing weighted on base average (wOBA, utilized to attempt to quantify the contribution that each hit plays rather than weighing each kind of hit or walk equally) and finding how that compares to the league overall. The more prominent statistic is wRC+, which is a league- and park-adjusted version of this statistic.
  • Wins Above Replacement (WAR) – A number that attempts to place a value on the number of wins that a player provides his team above the replacement-level player in the league. There are seemingly different formulas for each different WAR. Baseball Prospectus was the first to really address the statistic, and their version is called WARP (wins above replacement player). Fangraphs and Baseball-Reference each add in their own formulas, and when sourced in writing, you often see them abbreviated as fWAR for Fangraphs WAR and bWAR for Baseball-Reference’s WAR. The major differences in the calculations have to do with how each uses defense, whether a simple positional adjustment, using a metric measuring range against the rest of the league, or using something like defensive runs saved to weigh as the defensive factor in the calculation. Our Indians blog, Wahoos On First, did a quick and dirty WAR calculator if you’d like to play with how different statistics can affect the number.
  • Win Probability Added (WPA) – Statistic that attempts to measure the “story” of the game by weighing the game situation when a hit happens to give it extra weight.

Next: Pitching Terms