MLB Stat Glossary
Plain-language definitions for every stat SportStrata tracks, from basic counting stats to advanced Statcast metrics. Free, no login required.
- AVG
- Batting Average — hits divided by at-bats.
- BABIP
- Batting Average on Balls In Play — how often balls put in play fall for hits. Formula: (Hits minus Home Runs) divided by (At-Bats minus Strikeouts minus Home Runs plus Sacrifice Flies).
- Barrel%
- Barrel Percentage — share of batted balls classified as "barrels" (the optimal combination of exit velocity and launch angle).
- BB/9
- Walks per 9 Innings — walks allowed per 9 innings pitched.
- BB%
- Walk Percentage — share of plate appearances that end in a walk.
- CSW%
- Called Strike plus Whiff Percentage — share of pitches that result in either a called strike or a swinging strike. A composite command-and-stuff metric.
- ERA
- Earned Run Average — earned runs allowed per 9 innings pitched.
- EV
- Exit Velocity — average speed of the ball off the bat, in mph.
- FIP
- Fielding Independent Pitching — an ERA estimator using only home runs, walks, and strikeouts. Removes team defense from the equation.
- HH%
- Hard Hit Percentage — share of batted balls hit with an exit velocity of 95 mph or higher (Statcast).
- HR
- Home Runs.
- IP
- Innings Pitched.
- ISO
- Isolated Power — extra-base power. Formula: Slugging Percentage minus Batting Average.
- K-BB%
- Strikeout Percentage minus Walk Percentage — a composite command-and-stuff metric.
- K/9
- Strikeouts per 9 innings pitched.
- K%
- Strikeout Percentage — share of plate appearances that end in a strikeout.
- LA
- Launch Angle — average vertical angle of batted balls, in degrees.
- LOB%
- Left on Base Percentage — the share of a pitcher’s baserunners who do not score. Higher means a better ability to strand runners.
- OBP
- On-Base Percentage — how often a batter reaches base per plate appearance.
- OPS
- On-Base Plus Slugging (OBP + SLG).
- QS
- Quality Start — a start of at least 6 innings pitched with 3 or fewer earned runs allowed.
- QS%
- Quality Start Percentage — share of a pitcher’s starts that qualify as quality starts.
- RBI
- Runs Batted In.
- RC
- Runs Created — a Bill James formula estimating a hitter’s offensive contribution: (Hits plus Walks) times Total Bases, divided by (At-Bats plus Walks).
- RDIFF
- Run Differential — a team’s runs scored minus runs allowed.
- SB
- Stolen Bases.
- SB%
- Stolen Base Percentage — share of steal attempts that succeed.
- SLG
- Slugging Percentage — total bases per at-bat.
- Sprint Speed
- Sprint Speed — feet per second in a player’s best running situations.
- SS%
- Sweet Spot Percentage — share of batted balls hit with a launch angle between 8 and 32 degrees, the optimal contact zone.
- Whiff%
- Whiff Percentage — share of swings that miss entirely. Higher means more swing-and-miss stuff.
- WHIP
- Walks Plus Hits per Inning Pitched.
- wOBA
- Weighted On-Base Average — weights every way of reaching base by its actual run value. A more accurate offensive measure than on-base percentage alone.
- xBA
- Expected Batting Average based on exit velocity and launch angle (Statcast).
- xSLG
- Expected Slugging Percentage based on quality of contact (Statcast).
- xwOBA
- Expected Weighted On-Base Average based on quality of contact (Statcast).