Sports Analytics Glossary
Your comprehensive guide to sports analytics terms, metrics, and abbreviations
At Bat (AB)
An official batting appearance that counts toward a player's batting average, excluding walks, hit by pitches, sacrifice bunts, and sacrifice flies. At-bats are the denominator in calculating batting average and several other traditional statistics. A plate appearance that results in a walk or sacrifice does not count as an at-bat.
Average Fastball Velocity (vFA)
The average velocity of a pitcher's fastball measured in miles per hour by Statcast. Higher velocity correlates with better strikeout rates and fewer hard-hit balls, though command and pitch mix are also critical. The average major league fastball velocity has increased to around 93-94 mph in recent years.
BABIP (BABIP)
Batting Average on Balls In Play - measures how often balls in play fall for hits
Barrel Rate (Barrel%)
The percentage of batted balls that achieve optimal exit velocity and launch angle combinations, as defined by Statcast. Barrels represent the ideal contact outcomes with the highest likelihood of producing extra-base hits and home runs. A barrel rate above 10% is considered excellent and strongly correlates with power production.
Base Runs (BsR)
A run estimator formula that models the scoring process more accurately than linear weights approaches by accounting for the non-linear relationship between offensive events. It separates advancement on base from scoring opportunities, providing a more realistic estimate of runs created. Base Runs is considered one of the most accurate run estimation methods available.
Batting Average (AVG)
The ratio of a player's hits to their total at-bats, calculated by dividing hits by at-bats. It is one of the oldest and most traditional measures of batting performance. A .300 average is typically considered excellent in professional baseball.
Batting Average on Balls In Play (BABIP)
Measures how often a ball in play (excluding home runs) falls for a hit, calculated by dividing hits minus home runs by at-bats minus home runs minus strikeouts plus sacrifice flies. The league average BABIP typically hovers around .300, and extreme deviations often indicate luck that will regress. It helps identify whether a player's performance is sustainable or influenced by good or bad luck.
Caught Stealing Percentage (CS%)
The percentage of stolen base attempts that a catcher successfully throws out, calculated by dividing caught stealing by stolen base attempts. It measures a catcher's defensive contribution in controlling the running game. League average CS% is typically around 25-30%, with elite catchers maintaining rates above 35%.
Complete Game (CG)
A game in which a starting pitcher throws the entire game for their team, regardless of the outcome or number of innings in a shortened game. Complete games have become increasingly rare in modern baseball due to pitch count limits and specialized bullpen usage. They demonstrate stamina, efficiency, and dominance when achieved.
Contact Percentage (Contact%)
The percentage of swings that result in contact with the baseball, calculated by dividing swings with contact by total swings. Lower contact rates indicate better ability to generate swings and misses, which typically leads to more strikeouts. League average contact rate is around 75-77%, with elite pitchers maintaining rates below 70%.
Defensive Efficiency (DER)
The percentage of balls in play that are converted into outs by the defense, calculated by dividing outs on balls in play by total balls in play. It measures the overall defensive performance of an entire team rather than individual players. A higher DER indicates better team defense, with league average typically around .690-.700.
Defensive Runs Saved (DRS)
Estimates the number of runs a player saved or cost their team compared to an average fielder at their position. It incorporates various components including range, error prevention, outfield arm strength, and double play turning ability. Positive DRS values indicate above-average defense, with +10 DRS considered gold glove caliber.
Double Play Percentage (DP%)
For middle infielders, the percentage of double play opportunities that are successfully converted into double plays. It measures both range to reach ground balls and the ability to turn two quickly and accurately. Elite middle infielders combine strong DP% with high range factors to provide maximum value.
Earned Run Average (ERA)
The average number of earned runs a pitcher allows per nine innings pitched, calculated by dividing earned runs by innings pitched and multiplying by nine. It is the most traditional measure of pitching effectiveness, though it can be influenced by factors outside the pitcher's control. An ERA under 3.00 is typically considered excellent in modern baseball.
Exit Velocity (EV)
The speed of the ball off the bat measured in miles per hour.
Exit Velocity (EV)
The speed of the baseball as it comes off the bat after contact, measured in miles per hour by Statcast. Higher exit velocities correlate strongly with better offensive outcomes, as harder-hit balls are more likely to become hits. Elite hitters regularly produce average exit velocities above 90 mph.
Expected Fielding Independent Pitching (xFIP)
Similar to FIP but normalizes home run rate to league average based on fly ball rate, assuming that home run rates on fly balls tend to regress toward the mean. This accounts for the fact that HR/FB ratios fluctuate significantly year-to-year due to luck and sample size. xFIP is often considered more predictive of future performance than FIP.
Fielding Independent Pitching (FIP)
Estimates what a pitcher's ERA should be based only on outcomes the pitcher can control: strikeouts, walks, hit batters, and home runs. It removes the impact of defense and luck on balls in play, providing a more accurate measure of pitching skill. FIP is scaled to ERA for easy comparison, and FIP significantly lower than ERA suggests bad luck or poor defense.
Fielding Percentage (FPCT)
The percentage of chances handled successfully by a fielder, calculated by dividing the sum of putouts and assists by the sum of putouts, assists, and errors. While traditional, it is considered a poor measure of defensive ability because it doesn't account for range or plays not made. A fielder with limited range who makes no errors can have a perfect fielding percentage while providing poor defense.
FIP (FIP)
Fielding Independent Pitching - Measures what a pitchers ERA would be if they had average defense behind them.
First Pitch Strike Percentage (F-Strike%)
The percentage of plate appearances in which the pitcher throws a strike on the first pitch. Throwing first-pitch strikes is crucial for establishing favorable counts and maintaining control of at-bats. Pitchers with F-Strike% above 65% typically have better overall results, as hitters perform significantly worse when behind in the count.
Framing Runs (FRM)
Estimates the number of runs a catcher saves by receiving pitches in a way that influences umpires to call more strikes. Using Statcast data, it compares the actual called balls and strikes to the expected outcomes based on pitch location. Elite framers can save 15-20 runs per season, making it one of the most valuable defensive skills.
Games Started (GS)
The number of games in which a player was in the starting lineup at the beginning of the game. For pitchers, it specifically refers to games in which they were the starting pitcher who threw the first pitch. Games started is a basic counting statistic used to measure playing time and opportunity.
Ground Ball Rate (GB%)
The percentage of balls in play that are ground balls, calculated by dividing ground balls by total balls in play. Ground ball pitchers typically allow fewer home runs and generate more double plays, though they may allow more hits overall. A ground ball rate above 50% is considered high, while below 40% indicates a fly ball pitcher.
Hard Hit Percentage (Hard Hit%)
The percentage of batted balls hit with an exit velocity of 95 mph or greater, as measured by Statcast technology. Players with higher hard-hit rates are more likely to produce favorable offensive outcomes because hard-hit balls are more difficult for defenders to field. League average hard-hit rate is typically around 35-40%.
Hold (HLD)
A statistic credited to a relief pitcher who enters in a save situation, records at least one out, maintains the lead, and hands the game to another reliever without relinquishing the lead. Holds recognize the contributions of setup relievers who pitch in high-leverage situations but don't finish games. While useful for identifying key relief pitchers, holds don't capture the complete picture of reliever effectiveness.
Home Runs per Nine Innings (HR/9)
The average number of home runs a pitcher allows per nine innings, calculated by dividing home runs by innings pitched and multiplying by nine. Lower HR/9 rates indicate better ability to prevent hard contact and keep the ball in the park. League average HR/9 has increased in recent years to around 1.3-1.4.
Isolated Power (ISO)
Measures a hitter's raw power by calculating slugging percentage minus batting average. This isolates extra-base hits by removing singles from the equation, showing only a player's ability to hit for extra bases. An ISO above .200 is considered strong power, while .150-.200 is average.
Launch Angle (LA)
The vertical angle at which the ball leaves the bat.
Launch Angle (LA)
The vertical angle at which the ball leaves a player's bat after contact, measured in degrees by Statcast. A launch angle between 10-30 degrees is often optimal for producing line drives and fly balls that result in extra-base hits. Understanding launch angle helps evaluate a hitter's ability to elevate the ball and produce power.
Left on Base Percentage (LOB%)
The percentage of baserunners that a pitcher strands, not allowing them to score. League average is typically around 72%, and significant deviations often indicate luck that will regress toward the mean. Consistently high LOB% may indicate clutch performance or good sequencing, while low LOB% suggests bad luck or poor performance in high-leverage situations.
Leverage Index (LI)
Measures the importance of a particular game situation based on how much the outcome of the next play could change the team's win probability. A leverage index of 1.0 represents an average situation, while higher values indicate more critical moments like close games in late innings. LI is used to weight other statistics like WPA and identify clutch situations.
On-Base Percentage (OBP)
Measures how frequently a batter reaches base per plate appearance, including hits, walks, and hit-by-pitches. It is calculated by dividing the sum of hits, walks, and hit-by-pitches by the sum of at-bats, walks, hit-by-pitches, and sacrifice flies. OBP is considered more valuable than batting average because it accounts for a player's ability to draw walks.
On-Base Plus Slugging (OPS)
Combines on-base percentage and slugging percentage to provide a comprehensive measure of offensive production. It is simply the sum of OBP and SLG, giving equal weight to both getting on base and hitting for power. An OPS above .800 is generally considered very good, while above .900 is excellent.
OPS (OPS)
On-base Plus Slugging - Sum of on-base percentage and slugging percentage.
Outfield Arm Runs (ARM)
Measures the value of an outfielder's throwing arm in runs, based on their ability to prevent baserunners from advancing or to throw them out. It considers factors like arm strength, accuracy, and the context of throwing situations. Strong outfield arms can save several runs per season by deterring runners and making accurate throws.
Outs Above Average (OAA)
A Statcast metric that measures how many outs a fielder recorded compared to how many an average fielder would be expected to make, based on the catch probability of each play. OAA uses tracking data to calculate the precise difficulty of each opportunity based on factors like distance, direction, and hang time. It provides a direct count of extra outs made or missed.
Park Factor (PF)
A measure of how a ballpark affects offensive or defensive statistics compared to the league average, with 100 being neutral. Parks with factors above 100 favor offense (hitter-friendly), while below 100 favor pitchers. Park factors are crucial for properly evaluating player performance and making fair comparisons across different home stadiums.
Plate Appearance (PA)
Any completed batting appearance, including at-bats, walks, hit by pitches, sacrifice bunts, sacrifice flies, and catcher's interference. Unlike at-bats, plate appearances include all trips to the plate regardless of outcome. Modern statistics often use PA as the denominator because it provides a complete picture of a player's opportunities.
Pythagorean Win Expectation (PythWL)
Estimates a team's expected winning percentage based on runs scored and runs allowed using a formula similar to the Pythagorean theorem. Teams with significantly more wins than their Pythagorean expectation may have been lucky in close games, while teams with fewer wins may have been unlucky. It is useful for identifying teams that may regress or improve in future performance.
Quality Start (QS)
A starting pitcher performance in which they pitch at least six innings and allow three or fewer earned runs. Quality starts provide a simple measure of consistent, effective starting pitching performance. While useful, QS can be misleading as a 4.50 ERA over six innings qualifies, and dominant shorter outings do not.
Range Factor (RF)
Measures how many plays a fielder makes per nine innings, calculated by dividing the sum of putouts and assists by innings played and multiplying by nine. While simple, it can be misleading because it doesn't account for team factors like ground ball rate or the positioning of other fielders. Modern advanced metrics like UZR and DRS have largely superseded Range Factor.
Run Differential (RDIFF)
The difference between runs scored and runs allowed by a team, calculated by subtracting runs allowed from runs scored. Positive run differential indicates a team has scored more than they've allowed, while negative indicates the opposite. Run differential is highly predictive of team quality and often more accurate than win-loss record for evaluating true performance.
Run Expectancy (RE24)
Measures the change in run expectancy based on the 24 base-out states throughout a game, crediting players for increasing their team's expected runs. It captures context-dependent value by accounting for the specific game situations when events occurred. A player with high RE24 contributed significantly to their team's run-scoring opportunities in crucial situations.
Runs Created (RC)
An offensive statistic developed by Bill James that estimates the number of runs a player has contributed to their team. It combines various offensive statistics including hits, walks, total bases, and stolen bases into a single number. While more sophisticated metrics exist today, RC was pioneering in attempting to measure total offensive contribution.
Save (SV)
A statistic credited to a relief pitcher who finishes a winning game under specific conditions: entering with a lead of three runs or fewer, pitching at least one inning with any lead, or entering with the tying run on base, at bat, or on deck. Despite its prominence, the save statistic is considered flawed because it doesn't account for the difficulty of the situation or the quality of performance.
Secondary Average (SecA)
Measures a player's offensive contributions beyond batting average, including extra bases on hits, walks, and stolen bases while penalizing for caught stealing. It is calculated using the formula: (TB-H+BB+SB-CS)/AB. Secondary Average highlights players who contribute through power, patience, and speed rather than just contact hitting.
Shutout (SHO)
A complete game in which the pitcher allows zero runs, whether earned or unearned. Shutouts are one of the rarest achievements in modern baseball, requiring both excellence and durability from the starting pitcher. They represent the pinnacle of single-game pitching dominance.
Skill-Interactive ERA (SIERA)
An advanced pitching metric that estimates a pitcher's true talent level by incorporating strikeout rate, walk rate, ground ball rate, and their interactions. Unlike FIP, SIERA accounts for the fact that strikeouts are more valuable with runners on base and considers a pitcher's batted ball profile. It is designed to be more predictive of future ERA than FIP or xFIP.
Slugging Percentage (SLG)
Measures the total number of bases a player records per at-bat, emphasizing extra-base hits. It is calculated by dividing total bases by at-bats, where singles count as 1, doubles as 2, triples as 3, and home runs as 4. A higher slugging percentage indicates greater power hitting ability.
Strikeout Rate (K%)
The percentage of plate appearances that result in a strikeout, calculated by dividing strikeouts by total plate appearances. A lower K% is generally preferred as it indicates better contact ability and bat control. The league average K% has steadily increased in recent years, currently sitting around 23%.
Strikeout to Walk Ratio (K/BB)
The ratio of strikeouts to walks issued by a pitcher, calculated by dividing total strikeouts by total walks. A higher K/BB ratio indicates excellent command and the ability to miss bats while avoiding free passes. Elite pitchers typically maintain K/BB ratios above 4.0, while 2.5 is considered league average.
Strikeouts per Nine Innings (K/9)
The average number of strikeouts a pitcher records per nine innings, calculated by dividing strikeouts by innings pitched and multiplying by nine. Higher K/9 rates indicate better ability to miss bats and avoid putting balls in play. Modern elite pitchers typically maintain K/9 rates above 10.0.
Swinging Strike Rate (SwStr%)
The percentage of all pitches on which the batter swings and misses, calculated by dividing swinging strikes by total pitches. A higher SwStr% indicates better ability to generate whiffs and avoid contact. Elite pitchers typically maintain SwStr% rates above 12%, while league average is around 10-11%.
Triple Crown
An achievement for a batter who leads their league in batting average, home runs, and runs batted in during the same season. The Triple Crown is exceedingly rare, occurring only 17 times in Major League Baseball history, with Miguel Cabrera being the most recent in 2012. It represents the pinnacle of offensive dominance across multiple statistical categories.
True Average (TAv)
A rate statistic developed by Baseball Prospectus that measures a player's offensive contribution per plate appearance, adjusted for context. It is scaled to resemble batting average for easy interpretation, with .260 being average and .300 being excellent. TAv incorporates all offensive events weighted by their run values and adjusts for park and league factors.
Ultimate Zone Rating (UZR)
Measures a fielder's defensive contribution in runs above or below average, based on the number of plays made compared to the league average at their position in similar situations. UZR accounts for the difficulty and context of each play, including the location, type, and speed of balls in play. A UZR of +10 means the player saved 10 more runs than an average fielder.
Walk Rate (BB%)
The percentage of plate appearances that result in a walk, calculated by dividing walks by total plate appearances. A higher BB% indicates better plate discipline and the ability to work counts favorably. Elite hitters typically maintain BB% rates above 12%, while league average is around 8-9%.
Walks per Nine Innings (BB/9)
The average number of walks a pitcher allows per nine innings, calculated by dividing walks by innings pitched and multiplying by nine. Lower BB/9 rates indicate better command and control of pitches. Elite pitchers typically maintain BB/9 rates below 2.0, while league average is around 3.0.
Walks plus Hits per Inning Pitched (WHIP)
Measures the number of baserunners a pitcher allows per inning, calculated by adding walks and hits and dividing by innings pitched. It is a simple but effective measure of a pitcher's ability to prevent batters from reaching base. A WHIP below 1.00 is exceptional, while 1.30 or below is generally considered good.
WAR (WAR)
Wins Above Replacement - estimates how many wins a player adds compared to a replacement-level player
WAR (WAR)
Wins Above Replacement - A comprehensive statistic that estimates a players total contributions to their team in terms of wins.
Weighted On-Base Average (wOBA)
An advanced metric that weights different offensive outcomes based on their actual run value contribution. Unlike traditional stats, wOBA properly credits walks, singles, doubles, triples, and home runs according to their true offensive value. The scale is designed to mirror OBP, making it easy to interpret while being more accurate than OPS.
Weighted Runs Above Average (wRAA)
Measures how many runs a player contributes above or below league average based on their weighted offensive events. It is calculated by converting wOBA into runs and comparing to league average performance. A wRAA of +20 means the player created 20 more runs than an average player with the same number of plate appearances.
Weighted Runs Created Plus (wRC+)
Measures a player's total offensive value compared to league average, adjusted for park factors, where 100 is average. A wRC+ of 120 means the player created 20% more runs than an average player would have in the same number of plate appearances. It combines the accuracy of wOBA with park and league adjustments for easy comparison across eras and ballparks.
Win Probability Added (WPA)
Measures how much a player's actions change their team's probability of winning the game, with greater weight given to plays in high-leverage situations. A walk-off home run might add .500 WPA, while a solo home run in a blowout might add only .020 WPA. Unlike many stats, WPA is context-dependent and backward-looking rather than predictive.
Wins Above Replacement (WAR)
An all-encompassing statistic that attempts to measure a player's total contribution to their team in wins above a replacement-level player. It combines offensive, defensive, baserunning, and positional value into a single number, with different versions like fWAR and bWAR using slightly different methodologies. A WAR of 2.0 is considered average, 5.0 is all-star caliber, and 8.0+ is MVP level.
wOBA (wOBA)
Weighted On-Base Average - A rate statistic that measures overall offensive value.
wRC+ (wRC+)
Weighted Runs Created Plus - offensive value adjusted for park and league
Quick Reference
Common sports analytics metrics you should know
Baseball Metrics
- WAR - Wins Above Replacement
- wOBA - Weighted On-Base Average
- FIP - Fielding Independent Pitching
- wRC+ - Weighted Runs Created Plus
Soccer Metrics
- xG - Expected Goals
- xA - Expected Assists
- PPDA - Passes Per Defensive Action
- PSxG - Post-Shot Expected Goals
Basketball Metrics
- PER - Player Efficiency Rating
- TS% - True Shooting Percentage
- BPM - Box Plus/Minus
- VORP - Value Over Replacement Player
Football Metrics
- EPA - Expected Points Added
- CPOE - Completion Percentage Over Expected
- DVOA - Defense-adjusted Value Over Average
- PFF Grade - Pro Football Focus Grade