A baseball broadcast, box score or standings table can carry two dozen abbreviations on one screen. This glossary groups them by where you see them, gives the definition and the formula where there is one, and works through the numbers so you can check them yourself. Standard definitions follow the MLB.com glossary and the FanGraphs Library.
On the box score: batting
- AB (at-bats): plate appearances minus walks, hit-by-pitches, sacrifice bunts, sacrifice flies and catcher's interference. PA (plate appearances) counts every trip to the plate.
- R, H, RBI: runs scored, hits, runs batted in.
- BB, IBB, HBP: walks (bases on balls), intentional walks and hit-by-pitch.
- SF, SH: sacrifice fly and sacrifice hit (bunt). Neither counts as an at-bat.
- LOB (left on base): for a batter, the runners on base when he made an out and who stayed there. For a team, the runners stranded at the end of each half-inning, added up. A team LOB of 10 usually means plenty of chances and not enough big hits.
- RISP (runners in scoring position): runners on second or third. "2-for-9 with RISP" means two hits in nine at-bats with a runner on second or third.
- AVG/OBP/SLG (the slash line): batting average, on-base percentage and slugging percentage, written together, for example .280/.350/.480. OPS is OBP + SLG, so that line has an OPS of .830.
On the box score: pitching
- IP (innings pitched): the digit after the dot is outs, so 5.2 IP is five innings and two outs, or 17 outs in total. Our guide to reading pitcher stats shows why you convert before dividing.
- BF or TBF (batters faced): every plate appearance against the pitcher. It is the denominator for strikeout and walk rates.
- NP (number of pitches) and PC-ST (pitch count–strikes): "PC-ST 98-64" means 98 pitches, 64 of them strikes (called, swinging, fouls and balls put in play all count as strikes here). A strike share near 65% is normal for a big-league starter.
- ER, HR, K, BB: earned runs, home runs allowed, strikeouts and walks.
- W, L, SV, HLD, BS: win, loss, save, hold and blown save. The relief stats are explained in bullpen roles explained.
- GS, GF, QS: games started, games finished (the last pitcher of the game for his team) and quality starts (at least six innings with three or fewer earned runs).
On the broadcast
- MVR (mound visits remaining): how many trips to the mound a team has left. Since 2024 MLB allows four per team per nine innings (it was six in 2018 and five from 2019), plus one for each extra inning; visits to check an injury or after an offensive substitution do not count (MLB glossary).
- Pitch clock and timer: the countdown the pitcher has to start his motion. Running out of time is an automatic ball; a batter who is not ready is charged a strike.
- Velo, spin, IVB: pitch speed in mph, spin rate in revolutions per minute and induced vertical break (how much a pitch rises or sinks compared with a spinless ball), all from Statcast tracking.
- Whiff: a swing and miss. Whiff rate = whiffs ÷ swings. CSW (called strikes plus whiffs) = (called strikes + whiffs) ÷ pitches; around 30% is a strong mark for a starter, and our pitcher projections show it for every probable starter.
- Crooked number: any inning with two or more runs, so called because the scoreboard shows a figure other than 0 or 1.
Advanced stats you will meet online
- wOBA (weighted on-base average): an on-base stat that weights each way of reaching base by its run value, so a double counts for more than a single. It is scaled to look like OBP.
- wRC+ (weighted runs created plus): a hitter's run production adjusted for his ballpark and the league, where 100 is league average. A 130 wRC+ created 30% more runs than an average hitter would have in the same plate appearances; an 85 is 15% below average.
- FIP, xFIP, xERA: ERA estimators built from strikeouts, walks, home runs and contact quality. See FIP, xFIP and xERA explained.
- BABIP (batting average on balls in play): (H − HR) ÷ (AB − K − HR + SF). Swings with defense and luck in short samples.
- xBA, xwOBA: expected batting average and expected wOBA from exit velocity and launch angle (Statcast).
- WAR (wins above replacement): total value in wins compared with a freely available replacement player. Different sites use different formulas, so compare WAR within one source.
WPA: win probability added, worked through
Win probability is the chance a team wins from the current inning, score, outs and base runners. WPA credits each play with the change it causes. Say the home team trails by one in the bottom of the eighth with a runner on second and one out, and its win probability is 40%. The batter doubles in the tying run and the win probability jumps to 62%. The batter gets +0.22 WPA and the pitcher −0.22. Add a player's plays together over a game or a season and you get his WPA.
WPA tells a story about when things happened, not how well a player played in a neutral sense: a solo homer in a 9–1 game is worth almost nothing, while a bloop single in the ninth of a tie game can be worth +0.30. That is why it is used to describe games, while rate stats such as wRC+ and K% are used to predict them. Our explainer on what a win probability means covers how pregame probabilities are built and graded.
In the standings
- W, L, PCT: wins, losses and winning percentage (wins ÷ games). 90–72 is a .556 PCT.
- GB (games behind): ((leader's wins − team's wins) + (team's losses − leader's losses)) ÷ 2. A 90–72 team behind a 95–67 leader is ((95 − 90) + (72 − 67)) ÷ 2 = 5 games back.
- L10 and STRK: record over the last 10 games and the current streak (W3 = three straight wins).
- RS, RA, DIFF: runs scored, runs allowed and run differential.
- E-number: the elimination number, the combination of the leader's wins and the trailing team's losses that ends the race.
- X-W/L or Pythag: expected record from runs. Baseball-Reference uses W% ≈ RS^1.83 ÷ (RS^1.83 + RA^1.83). A team scoring 750 and allowing 650 runs projects to about .565, or roughly 91–92 wins over 162 games.
A quick decoding exercise
A starter's line reads 5.2 IP, 6 H, 2 ER, 1 BB, 7 K, NP 97, PC-ST 97-63, 24 BF. That is 17 outs, a strike share of 63 ÷ 97 = 65%, a strikeout rate of 7 ÷ 24 = 29.2% and a walk rate of 1 ÷ 24 = 4.2%. The ERA for the outing is 9 × 2 ÷ 5.667 = 3.18. The strikeout and walk rates are the part that predicts the next start best, which is why the projection model leans on them.
For more on reading these numbers without fooling yourself, see common mistakes reading baseball stats.