Upcoming Match-ups

Most Common Baseball Stats Abbreviations

Mitchell South

by Mitchell South

Updated May 6, 2024 · 1:32 PM PDT

When it comes to betting on baseball, it pays to know your numbers. More than any other sport, the pace and structure of MLB baseball suits itself perfectly to detailed statistical analysis.

For the uninitiated, a first glance at MLB stats can be an overwhelming experience. With so many acronyms and abbreviations, it’s easy to get a bit confused.

This comprehensive glossary will help you quickly grasp the abbreviations used to describe complex MLB team and player stats.

Note that Major League Baseball records each of these stats for both individual players and every team collectively.

Traditional Stats

Traditional player stats have been collected from the beginning of MLB history. These numbers tend to focus on a single element of an individual player’s performance.

When betting on baseball, they are useful in evaluating the situational performance of both individual players and entire teams.

Traditional Baseball Stat Abbreviations – Batting

G – Games played: The number of games the player has appeared in during the current MLB season.

AB – At bats: The number of times the player has been at bat, defined as plate appearances minus sacrifices, walks, and Hit by Pitches.

R – Runs: The total number of runs the player has scored as a baserunner (safely reaching home plate).

H – Hits: The total number of times a player hits the ball and reaches a base without fielder error or sacrifice.

2B – Doubles: The number of times a player hits the ball and safely reaches second base without fielder error or sacrifice.

3B – Triples: The number of times a player hits the ball and safely reaches third base without fielder error or sacrifice.

HR – Home runs: The number of home runs a player has hit. These include inside-the-park home runs.

RBI – Runs Batted In: The overall number of runs scored as a direct result of a player hitting the ball or being walked when at-bat.

BB – Bases on Balls: The number of times a player is ‘walked’ or awarded first base after four balls are thrown during an at-bat.

SO – Strikeouts: The number of times a player strikes out while at bat.

SB – Bases Stolen: The total number of bases a player has stolen as a baserunner.

CS – Caught Stealing: The total number of times a player has been thrown out while attempting to steal bases as a baserunner.

AVG – Batting Average: Describes the percentage of time a batter has successfully made a hit while at bat during the current season. Defined as hits divided by at bats (H/AB), this is the most common traditional stat used to compare hitting ability.

OBP – On-Base Percentage: Describes the percentage of time a batter advances to base as a result of hit, walk, or hit-by-pitch. Defined as (H+BB+HBP)/(AB+BB+HBP+SF), the stat provides a good general indicator of a player’s likelihood to reach base during an average at-bat.

SLG – Slugging Percentage: Describes a player’s power and productivity as hitter, as defined by total bases divided by at bats (TB/AB). Valuable for evaluating not only how often a player is likely to get a hit, but also the quality and relative value of those hits. Players with higher SLG are more likely to hit doubles, triples, and home runs.

IBB – Intentional Base on Balls: Also known as intentional walks, the total number of times a batter is intentionally given first base after four balls deliberately thrown by the pitcher. High IBB is a strong indirect indicator of slugging ability.

HBP – Hit by Pitch: The number of times a player has been hit by a pitch while at bat during the current season. A high HBP may indicate a player who ‘crowds the plate’ or takes an excessively inside batting stance. Subjective observations may be a better indicator of a player’s batting stance.

SAC/SH – Sacrifice Bunts: The number of ‘sacrifice bunts’ or ‘sacrifice hits’ a player has made throughout the season. Only successful sacrifices are counted, so a baserunner must advance in order for the sacrifice to be tallied.

SF – Sacrifice Flies: The number of times during the season a player has hit a fly-ball to the outfield or foul territory that allows a baserunner to score but results in an out for the player at bat.

TB – Total Bases: The total number of bases a player has taken with their batting; tallies one for singles, two for doubles, three for triples.

XBH – Extra Base Hits: The total number of hits other than singles. Long hitters tend to have higher XBH values.

GDP/GIDP – Ground into Double Play: The number of times a player has hit a ground ball that results in multiple outs on the bases. Double plays most often occur as a result of balls pitched low in the strike zone, which typically result in ground balls that do not leave the infield.

GO – Ground Outs: The number of times a player has hit the ball and grounded out during the current season.

AO – Fly Outs: The number of times a player has hit a fly ball that was caught for an out. This number does not include line drives.

GO_AO – Ground Out to Air Out Ratio: The ratio of ground outs vs fly outs for a player during the given season. This ratio is not particularly useful as a handicapping tool.

NP – Number of Pitches: When referring to a position player, NP indicates the total number of pitches thrown during their at-bats.

PA – Plate Appearances: The number of completed turns at the plate a player has taken throughout the season. Unlike at-bats, which do not include plate appearances with certain results, PA tallies every single plate appearance regardless of outcome.

Traditional Baseball Stat Abbreviations – Pitching

APP – Appearance: The number of games in which a pitcher enters the game. Pitchers are credited with an appearance regardless of when they enter the game or how many batters they face throughout.

BK – Balk: The number of ‘balks’ a pitcher has accrued throughout the season. A balk occurs when the umpire calls the pitcher for an illegal and deceitful motion on the mound. All baserunners advance one base when a balk is called.

BF – Batters Faced: The total number of plate appearances the pitcher has faced during the season. This number is a good indicator of a pitcher’s longevity once entering or starting a game.

BS – Blown Save: This statistic is specific to relief pitchers and tallies the number of games in which they enter in a save situation to ultimately allow a tying run to score. BS is very valuable in judging the ability of a closer to perform in a high-pressure situation.

CG – Complete Game: The number of start-to-finish games pitched. Complete games are exceedingly rare in modern baseball and indicate an exceptional game by a talented pitcher with incredible stamina.

ER – Earned Run: The number of runs scored against a pitcher that do not benefit from either a fielding error or passed ball. This stat allows bettors to isolate the pitching performance as a factor contributing to the other team’s final score.

ERA – Earned Run Average: Easily the most widely referenced pitching stat, ERA indicates the average number of earned runs conceded per nine innings pitched.

When comparing pitchers across leagues, note that ERA values in the NL tend to be significantly lower thanks to lack of designated hitters in the batting lineup.

ERA tends to be more useful when measuring the abilities of starters vs relief pitchers.

AO – Flyout: The total number of outs that occur as a result of a batter hitting a caught fly ball. Pitchers who induce lots of fly balls tend to pitch higher in the zone. This makes them vulnerable to power hitters who can easily knock a high ball over the wall.

GF – Games Finished: Primarily a stat for closers, GF tallies the number of games in which a pitcher was the last pitcher to take the mound for their team.

GS – Games Started: GS tallies the total number of games in which a pitcher throws the first pitch for their team, regardless of how many at-bats or innings they remain in the game.

GO – Groundout: The total number of outs that occur as a result of a batter hitting a ground ball to a fielder. Pitchers who tally large amounts of groundouts likely tend to throw lower in the strike zone.

HLD – Hold: This relief pitcher stat tallies the number of games in which a reliever enters the game in a save situation and maintains their team’s lead until they are relieved by another pitcher, so long as they record at least one out.

HLD is helpful in identifying strong relief pitchers who typically enter the game earlier or do not serve as closers.

IP – Innings Pitched: Pitchers are credited a third of an inning pitched for each out recorded while they are on the mound.

It is very difficult to rank highly in terms of innings pitched without being a strong starter with the ability to pitch deep into a ballgame.

L – Loss: Pitchers receive a loss when they are attributed a run that gives the opposing team a lead from which their team is unable to recover.

Note that a starter will not necessarily be credited a loss every time his team loses the game he starts, even if his team is trailing when he exits the game. Only the pitcher who puts the winning run on-base will be credited a loss.

Both wins and losses are not particularly accurate indicators of a pitcher’s ability. Because these statistics do not account for elements of the game out of the pitcher’s control, they are only loosely descriptive of a pitcher’s overall ability and value to their team.

Stick with ERA and advanced stats when comparing pitching ability.

NP – Number of Pitches: NP is a comprehensive pitch count that includes every single pitch thrown, regardless of outcome.

If you know a pitcher’s average Pitches Per Start (P/GS), you can keep an eye on NP to determine when they are likely to grow tired and eventually be pulled from the game.

PK – Pickoff: PK tallies the number of baserunners a pitcher ‘picks off’ by throwing the ball to the fielder guarding the bag of a baserunner who has led off the plate before the runner can return to tag the plate.

QS – Quality Start: QS provides an objective measure of the number of games in which a starter puts in a respectable performance. Starters are credited a QS when they pitch at least six innings and allow three or fewer earned runs.

Note that pitchers skirting the line by allowing three runs over six innings are not putting in stellar performances. It’s worth considering the wider context and individual performances when using QS to handicap pitching abilities.

SV – Save: Relief pitchers are credited with a save when finishing the game for a winning team, under certain circumstances.

To be credited a save, the relieving pitcher must keep his team ahead in one of the three following circumstances:

  1. Enter the game with a lead or three runs or less and pitch at least one complete inning.
  2. Enter the game with the tying run on-deck, at-bat, or on the bases.
  3. Pitch at least the final three innings.

SVO – Save Opportunity: Relief pitchers are credited with a save opportunity every time they record either a save or blown save.

Pitchers with a high SVO tally are often put in high-pressure game situations, indicating their managers have a great deal of faith in their abilities to maintain a crucial lead late in the game.

SV% – Save Percentage: SV% is an excellent metric to evaluate a closer’s ability to get the job done. This stat records the percentage of time a pitcher is credited a save when given a save opportunity.

SV% is considered the most useful number to compare closers because it accounts for differences in the number of games a closer enters. Strictly comparing saves does not account for the fact many(? teams present their bullpen more save opportunities than others.

SHO – Shutout: Starters receive a shutout when they pitch an entire game and do not allow the other team to score. Shutouts are exceedingly rare, particularly in the modern era of baseball, where teams have become increasingly reliant on their bullpens.

SO/K – Strikeouts: The number of times a pitcher throws three strikes, resulting in an out before a batter can hit the ball or is walked to first base.

UER – Unearned Runs: Unearned runs are attributed to a pitcher when the other team scores as the result of a fielding error or passed ball.

WHIP – Walks & Hits Per Inning Pitched: WHIP is calculated by finding the sum of a pitcher’s walks and hits divided by their total innings pitched.

As a comprehensive number capturing a pitcher’s ability to prevent batters from reaching the basepath, WHIP is one of the best metrics for a pitcher’s overall defensive value.

WP – Wild Pitches: Wild pitches are tallied anytime a pitcher delivers a ball that the catcher is unable to control, resulting in the advancement of at least one baserunner. Note that wild pitches are only recorded when they result in the advancement of a runner.

Wild pitches are closely related to passed balls (PB), which have a similar result but are deemed to be the fault of the catcher.

W – Wins: Pitchers are credited with a win when they are on the mound when their team takes the game-winning lead. In order to qualify for a win, the pitcher must also pitch at least five innings.

WPCT – Winning Percentage: Winning percentage indicates the percentage of the time that a pitcher is credited with a win when they are the ‘pitcher of record.’

The pitcher credited with a W or L is the ‘pitcher of record’ for a given MLB game. This stat, along with other pitching stats derived from wins and losses have fallen out of favor with baseball handicappers since pitching ability does not correlate directly with wins and losses.

Traditional Baseball Stat Abbreviations – Fielding

A – Assist: Fielders are awarded an assist when they touch the ball before a putout is recorded by one of their teammates. This scenario most often occurs when a ball is fielded by one player and thrown to another (as is the case with most ground balls).

CS% – Caught Stealing Percentage: The percentage of the time a catcher throws out opposing baserunners who are attempting to steal a base.

DP – Double Plays: Double plays are recorded when two offensive players are called out as the result of a single defensive play. Most often, this occurs when a ground ball is fielded with a runner on first and both the existing baserunner and hitter are thrown out.

E – Error: Players receive an error when they fail to force an out on a play that an average fielder would have made, or when they make a fielding mistake that allows one or more baserunners to advance.

Remember that errors are a counting statistic, meaning they only tally the mistakes a fielder has made with no regard for their positive contributions.

FPCT – Fielding Percentage: This is a comprehensive stat that evaluates a fielder’s success rate each time they are presented with an opportunity to make a play.

It is defined by calculating the total number of putouts and assists a player has made divided by the total number of fielding chances (to include putouts, assists, and errors).

Note that position plays a huge role in this number – catchers and first basemen are typically presented with easier play opportunities than shortstops and third basemen. Account for these differences when comparing the FPCT of fielders playing different positions.

INN – Innings Played: INN is tallied by counting the number of outs during which a player is on the field and dividing by three. It is a useful metric when determining how much playing time a given player gets on the defensive side of the ball.

O – Outs: Teams or players record an out every time a player at bat or running the bases is retired by the fielding team as the result of a strikeout, groundout, or caught flyout.

OFA – Outfield Assist: Outfielders are credited with an assist anytime they throw a fielded ball to the infield resulting in an out.

Outfield assists are generally used as a metric of an outfielder’s arm strength and general throwing ability.

PB – Passed Ball: Passed balls are closely related to wild pitches, but center on the performance of the catcher rather than pitcher.

Catchers record a passed ball anytime they fail to catch or control a pitch the official scorekeeper does not deem as a wild pitch.

PO – Putout: Fielders record a putout when they are the player to physically complete an out by stepping on base, tagging a runner, or catching a fly ball.

Putouts are rarely used as an independent fielding metric, but they are an important input used to formulate a number of advanced fielding stats (such as?).

TC – Total Chances: Total chances tallies the number of opportunities a fielder has to record an out, defined as assists plus putouts plus errors.

Like putouts, it’s primarily recorded for use as an input for other statistics, including FPCT.

TP – Triple Plays: A team records a triple play when three outs are achieved with a single defensive play. These events are exceedingly rare, and are a mark of a highly coordinated fielding unit.

Advanced Stats (Sabermetrics)

In recent decades, baseball statistics have been entirely overhauled by the advent of advanced formulas and calculations that attempt to capture detailed predictive insights about player performance and game scenarios.

Widely popularized by the filmMoneyball, sabermetrics have become an instrumental part of both team management and baseball handicapping. While some skeptics find them overly abstract, they’ve been generally embraced by Major League Baseball and those who know most about the game.

Advanced Baseball Stat Abbreviations – Batting

BABIP – Batting Average on Balls in Play: BABIP calculates a player’s batting average on balls hit into the field of play, excluding at bats that result in strikeouts, walks, or home runs.

When compared alongside AVG, this metric provides more context as to the type of hits a batter most often hits.

ISO – Isolated Power: ISO is used to identify power hitters by creating a batting average to include only extra-base hits. Triples are weighted more heavily than doubles, and home runs are weighted more heavily than triples.

Players with high ISO values can be expected to be very strong batters who often rank highly in terms of home runs.

OPS+ – On-Base Percentage + Slugging Plus: OPS+ attempts to normalize every player’s OPS rating across the entire league, accounting for external factors like ballparks and weighting numbers to as a perfect league average.

OPS+ simply improves the accuracy of OPS by adjusting for external factors, making it one of the best metrics bettors can use to evaluate a player’s potential at the plate.

P/PA – Pitches Per Plate Appearance: P/PA simply averages the number of pitches a batter faces when they take the plate.

Teams with a batting lineup full of hitters with high P/PA numbers are likely to wear out opposing pitchers more quickly, forcing the opposing team to rely more heavily on their bullpen.

RC – Runs Created: Runs created uses a complex formula to estimate the number of runs an individual player has contributed to their team. It relies on a player’s ability to get on base and hit for extra bases, compared to their total opportunities.

wRAA – Weighted Runs Above Average: wRAA estimates how many runs a player has contributed versus the expected contributions of an average player.

wOBA – Weighted On-Base Average: wOBA records a player’s on-base average while also accounting for how they reached base.

Methods of reaching base that are considered to have higher scoring potential are weighted more heavily. wOBA is highly productive (predictive?) of a player’s overall offensive efficiency.

wRC+ – Weighted Runs Created Plus: This weighted version of RC makes adjustments for external factors such as ballpark, making it a more accurate metric to use when comparing players from different teams or eras.

WAR – Wins Above Replacement: WAR is a comprehensive stat that attempts to capture the totality of a player’s contributions, expressed as the number of wins they’ve contributed to their team’s overall record versus a ‘replacement’ player.

Advanced Stats (Sabermetrics) – Pitching

ERA+ – Adjusted Earned Run Average: ERA+ normalizes ERA across the entire league, accounting for factors like ballparks and the strength of competition.

By accounting for ballpark, ERA+ can provide a more accurate indicator of each pitcher’s relative abilities.

MB/9 – Baserunners Per Nine Innings Pitched: MB/9 tallies the average number of baserunners a pitcher allows per nine innings pitched. This includes batters who reach base via hits, walks, and hit-by-pitches.

BQR – Bequeathed Runners: BQR tallies the number of runners left on base when a pitcher exits the game.

BQR-S – Bequeathed Runners Scored: BQR-S tallies the number of bequeathed runners who go on to score once a pitcher has exited the game.

FB% – Flyball Rate: The percentage of balls hit into play that are categorized as fly balls (which must reach the outfield).

High fly ball rates can be predictive of a pitcher’s tendency to allow lots of home runs.

GB% – Groundball Rate: The percentage of balls hit into play that are characterized as ground balls.

Ground balls tend to produce outs and double plays, making a high GB% desirable for most pitchers.

H/9 – Hits Per Nine Innings: H/9 calculates the average number of hits allowed per nine innings pitched.

HR/9 – Home Runs Per Nine Innings: HR/9 calculates the average number of home runs allowed per nine innings pitched.

IR-A – Inherited Runs Allowed: IR-A records the number of inherited runners who go on to score following a relief pitcher’s entrance to the game.

Note that strong relievers may have higher IR-A rating because they often enter the game in high-pressure situations with multiple runners on base.

I/GS – Innings Per Start: I/GS calculates the average number of innings a starting pitcher will throw before exiting the game.

High I/GS rating indicate a highly successful pitcher who is also consistent. These pitchers allow more rest for their team’s bullpen and tend to be highly efficient.

LD% – Line Drive Rate: The percentage of balls hit into play categorized as line drives.

Line drives are excessively difficult to field, making a high LD% of the biggest red flags when evaluating pitching ability.

PO% – Pop Up Rate: The percentage of balls hit into play categorized as pop ups, which are similar to fly balls but do not reach the outfield.

Pop ups are easily fielded, but often go hand-in-hand with a high flyball rate, a markedly negative indicator of pitching ability.

RS/9 – Run Support Per Nine Innings: RS/9 helps statisticians and bettors isolate a pitcher’s contributions by accounting for the help they receive from their team’s offensive efforts.

RS/9 calculates how many runs the pitcher’s team scores while they are in the game, adjusted for nine innings of play.

K% – Strikeout Rate: K% indicates the percentage of the time that a pitcherretires batters with a strikeout, defined as total strikeouts divided by total number of batters faced.

K/BB – Strikeout to Walk Ratio: K/BB provides a ratio that compares how frequently a pitcher records strikeouts vs walks.

tERA – True Earned Run Average: tERA attempts to improve the accuracy of ERA measurements by accounting for the quality of hits recorded against a pitcher.

In this sense, it more accurately captures the positive contributions of pitchers who frequently induce weak contact.

BB% – Walk Rate: The percentage of the time a pitcher walks batter, defined as total walks divided by total batters faced.

BB% is considered the most accurate method of determining the frequency with which a pitcher tends to put batters on base by walk.

Advanced Baseball Stat Abbreviations (Sabermetrics) – Fielding

DER – Defensive Efficiency Rating: DER evaluates a team’s overall fielding abilities, defined as rate which with batters reach base after putting the ball in play.

DER is generally considered the most solid comprehensive metric for evaluating team defense and directly comparing the fielding abilities of two teams.

DRS – Defensive Runs Saved: DRS attempts to capture the totality of a player’s defensive contributions in terms of number of runs saved.

The metric accounts for a wide range of factors including errors, range, outfield arm, and double-plays. By looking at a team’s collective DRS, bettors can get a general sense of how much defensive help pitchers can expect to enjoy from their fielders.

RF – Range Factor: RF is used to evaluate a fielder’s versatility and ability to convert plays into outs, defined by dividing the sum of their putouts and assists by the total number of defensive games played.

Note that defensive positioning can have a large impact on range factor, so it should also be considered in the wider context of a player’s field position and the tendencies of their team’s pitching lineup.

UZR – Ultimate Zone Rating: Like DRS, UZR attempts to quantify the totality of a player’s defensive capabilities in terms of number of runs saved.

The concept of these metrics is the same, but the formula to calculate them differs slightly. Take a look at both when comparing two players to get a second data-driven opinion on each player’s overall fielding abilities.

Looking for More Baseball Betting Resources?

The plethora of baseball stats available make it a particularly enticing game for sports bettors. Make sure you’re taking full advantage of the numbers outlined here and other sports analytics and team trends. See the latest ESPN Bet promo to get the best sign-up bonus at ESPN BET.

If you’re devouring stats across a number of sports, make sure you have our sports abbreviations glossary at the ready.

For baseball-specific betting advice, check out the tips and tricks in the MLB section of our how to bet on sports series.


Let's have fun and keep it civil.