Table 2.

Advanced Pitching Statistics Collected by the MLB Statcast System ^a

Statistic	Definition
Pitch velocity	How hard, in miles per hour, a pitch is thrown
Spin rate	How much spin, in revolutions per minute, a pitch has
Active spin	The spin that contributes to movement
Exit velocity (mean and maximum)	How fast, in miles per hour, a ball is hit by a batter
Launch angle	How high/low, in degrees, a ball is hit by a batter
Barrels %	Percentage of batted balls with the “perfect combination of exit velocity and launch angle”
Hard hit %	Percentage of balls hit with an exit velocity ≥95 mph
Whiff %	Percentage of swings and misses by total swings
Pitch movement (horizontal and vertical)	The movement of a pitch defined in inches; recorded in raw numbers and against average
Expected batting average	Measures the likelihood that a batted ball will become a hit
Expected weighted on-base average	Formulated using exit velocity, launch angle, and on certain types of batted balls, sprint speed
Expected ERA	1:1 translation of expected weighted on-base average, converted to ERA scale
Pitch selection (pitch %)	Percentage of each pitch thrown by pitch type

^a All definitions are from http://baseballsavant.mlb.com. ERA, earned run average; MLB, Major League Baseball.