Estimate perceived velocity
Your perceived velocity will appear here.
Built for a regulation 60 foot 6 inch mound. Release extension comes from a pitch tracker such as TrackMan, Rapsodo or Statcast. Nothing you type leaves your browser. Pitch AI itself is not a radar gun and does not measure velocity or extension.
What perceived velocity and extension mean
MLB's Statcast glossary describes perceived velocity as "an attempt to quantify how fast a pitch appears to a hitter, by factoring the Velocity of the pitch and the release point of the pitcher," and gives the example that a 95 mph fastball "will reach a hitter faster if the pitcher releases the ball seven feet in front of the rubber instead of six." Extension is how far in front of the rubber the pitcher releases the ball. The glossary notes that a pitcher with long extension "can make a 93 mph fastball look like a 96 mph fastball."
Statcast compares each pitcher with an average release point. Release in front of it and your perceived velocity is higher than your radar reading. Release behind it and it is lower. MLB.com's 2016 example: Carter Capps, with about 8 feet 4 inches of extension, turned 98.1 mph into 101.7 mph perceived, while Wily Peralta, at about 4 feet 11 inches, dropped from 90.2 to 87.6 mph.
How this calculator works
MLB has not published its exact formula, and Grantland noted in 2015 that the method was kept "close to the vest." The idea in the glossary is time to the plate, so this calculator uses a time-to-plate model:
perceived velocity = velocity x (59.08 - reference extension) / (59.08 - your extension)
- 59.08 feet is the distance from the rubber to the front edge of home plate: 60 feet 6 inches to the back tip, minus the 17-inch plate.
- The reference extension of 6.4 feet is where perceived velocity equals actual velocity. We checked it against public Baseball Savant pitch data, where Statcast's effective speed matched this model within about 0.4 mph on average. It also reproduces the Capps and Peralta numbers above to within 0.1 mph.
- Drag slows a pitch by several mph before it reaches the plate. Physicists Kagan and Nathan (2014) showed an 84 mph pitch dropping to about 77 mph. Because the slowdown is a similar percentage for most pitches, it largely cancels out in the ratio, but pitches with unusual drag can be off by a few tenths.
A useful rule of thumb falls out of the formula: near average extension, each extra foot adds about velocity divided by 53. That is roughly 1.7 mph at 90 mph and 1.8 mph at 95, in line with the 1.7 mph per foot that Rockland Peak Performance reported from MLB data.
Statcast's definition is for a 60 foot 6 inch mound. On 46, 50 or 54 foot mounds the same physics applies, but there is no official perceived velocity, and comparing a youth reading with MLB numbers is apples to oranges. For young pitchers, focus on the development that drives both velocity and extension.
Can you train extension?
Some of it. Extension depends heavily on height, arm length and stride, so a 6 foot 5 inch pitcher will usually release closer to the plate than a 5 foot 10 inch pitcher. The trainable parts are how well you move down the mound and how well your front leg accepts and stops that movement. Those same qualities show up in the research on velocity: pitching velocity biomechanics covers the lead leg block and stride in detail.
- Build the base first. Lower-body strength and hip mobility let a pitcher stride out and still stabilize. Forcing a longer stride without them often costs timing and command.
- Check it on video. Film from the side before and after a change. If extension goes up but the arm is late or the head drifts, the change is not helping.
- Do not trade velocity for extension. One more foot is worth under 2 mph of perceived velocity. Losing 2 mph of real velocity to get it is a bad deal.
Extension also interacts with pitch shape. Fastball ride, release height and arm slot change how a fastball plays, which is why extension is one input in pitch design rather than a goal on its own. Read more in how to throw a four-seam fastball and what pitches fit each arm slot.
Frequently asked questions
What is perceived velocity in baseball?
MLB's Statcast glossary describes perceived velocity as an attempt to quantify how fast a pitch appears to a hitter, by factoring in the pitch's velocity and the pitcher's release point. A pitcher who releases the ball farther in front of the rubber than average has a higher perceived velocity than his radar reading, and one who releases it behind average has a lower one.
How much does one foot of extension add to perceived velocity?
About 1.7 to 1.8 mph per foot for a 90 to 95 mph fastball, and less at lower speeds, roughly velocity divided by 53. Rockland Peak Performance reported a similar figure of about 1.7 mph per foot from MLB data.
What is the average extension in MLB?
Roughly 6 to 6.5 feet, depending on the season and pitch type. Average release extension has crept up in recent seasons. This calculator uses 6.4 feet as the reference, the point where Statcast perceived velocity equals actual velocity in our fit.
Is this the official Statcast formula?
No. MLB has not published its formula. This calculator uses a time-to-plate model with a typical drag assumption, fitted to Statcast effective speed values, and it reproduces published examples within a few tenths of a mph. Treat results as estimates.
How can a pitcher increase extension?
Extension mostly comes from body size, stride length and how well the pitcher moves down the mound and stabilizes on the front leg. Chasing extension with cues alone can disrupt timing, so work on lower-body strength, mobility and sequencing, and check the change on video rather than forcing a longer stride.
From numbers to a plan
Turn your pitch data into a plan with Pitch AI
Pitch AI does not measure velocity or extension. It works with the data you already have: import TrackMan, Rapsodo, Yakkertech, FlightScope or PitchLogic CSV exports (or a screenshot) into the pitch design tools for arsenal recommendations, get AI video feedback on your mechanics, and follow a throwing and strength program built for your level and season phase.
Sources and further reading
- MLB.com Statcast glossary: Perceived Velocity
- MLB.com Statcast glossary: Extension
- Baseball Savant: Statcast search CSV documentation (effective_speed, release_extension)
- Petriello M. How Thor, Fernandez make fastballs look faster. MLB.com, 2016
- Grantland: Actual versus perceived velocity and Statcast pitcher data (2015)
- Kagan D, Nathan AM. Simplified Models for the Drag Coefficient of a Pitched Baseball. The Physics Teacher, 2014
- Rockland Peak Performance: Extension at release, why it's important and how to maximize it