Resources
Definitions of the terms and metrics used by the Pitch Viewer.
Pitch Classification
The pitch classification is an estimate made from the measured release speed and the Magnus break (the deviation from the gravity-and-drag path) as seen from the pitcher's perspective. It is tuned for adult college and MLB pitchers and cannot detect gyro (bullet) spin, so sliders, cutters and sweepers are the least reliable.
Arm side is the throwing-hand side. It is only used when the pitcher handedness is provided in the pitch data; otherwise only the direction of the break is reported.
| Classification | Speed | Vertical Magnus | Lateral break |
|---|---|---|---|
| Curveball (topspin) | 65–88 mph | −8 in or lower | any |
| Topspin breaking ball | 65 mph and up | −3 to −8 in | any |
| Four-seam fastball | 88 mph and up | +12 in or more (backspin) | less than 8 in either side |
| Two-seam fastball / sinker | 86 mph and up | above −3 in | 8 in or more arm side |
| Cutter | 86 mph and up | below +6 in | 2 in or more glove side |
| Changeup | 65–86 mph | +2 in or more | 8 in or more arm side |
| Slider | 65–86 mph | +2 in or less | 3 in or more glove side |
Pitches that fit none of these are reported as undetermined. Pitches below 65 mph are not classified.
Release Speed
The ball speed in mph at the start of the tracked flight, taken from the first sensor interval. It is a measured speed, not the speed at the pitcher's hand.
Average Speed
The average ball speed in mph over the whole tracked distance from the first sensor to the plate. It is lower than the release speed because drag slows the ball.
Release Angle
The vertical angle in degrees of the initial flight direction, relative to horizontal. Positive is upward and negative is downward.
Release Horizontal Angle
The horizontal angle in degrees of the initial flight direction, relative to the line toward the target, as seen in the top view. It sets the straight release line the ball would follow without lateral break.
Lateral Break
The sideways distance in inches between the measured path and the straight release line at the end of the pitch, in the top view. The sign shows the direction: positive is toward the pitcher's right and negative toward the pitcher's left.
Gravity Drop
The vertical distance in inches the ball falls below the straight release line because of gravity by the end of the pitch. Magnus break is measured relative to the gravity and drag path, so it is separate from this value.
Magnus Vertical
The signed vertical difference in inches between the measured path and the gravity and drag-extrapolated path at the end of the pitch. Positive means the ball finished higher than gravity and drag alone predict (backspin lift). Negative means it finished lower (topspin sink). See also Peak Magnus Deviation, which is the largest unsigned vertical gap anywhere along the pitch.
Spin Classification
A label for the vertical spin effect, based on the sign and size of the Magnus vertical value, for example "Back Spin (Rise)". It describes the vertical effect only. For a pitch-type estimate, see Pitch Classification.
Spin Direction
The spin clock shows the direction the ball face seen by the pitcher is spinning, estimated from the vertical and lateral Magnus break. Backspin points down (about 6:00), topspin points up (about 12:00). The Magnus force acts opposite the arrows.
Peak Magnus Deviation
The maximum vertical deviation of the measured trajectory from the gravity and drag-extrapolated path, anywhere along the pitch. It is unsigned and can occur mid-flight, unlike the Magnus vertical value, which is the signed difference at the end of the pitch.
Estimated Release Point
Extrapolated backward from the first sensor to a release point 6 ft in front of the front edge of the mound (726 in from home plate). The first sensor is 568 in from home plate. It is an estimate and its uncertainty grows with the extrapolation distance.