What Stuff+ means
Stuff+ estimates how good a pitch is before a hitter ever swings at it. A computer model looks at the pitch's physical traits, such as velocity, induced vertical break, horizontal break, spin rate, spin axis, release height, and extension. It compares that pitch with a large database of similar pitches and how hitters did against them. The result is scaled so that 100 is league average and higher numbers are better.
The model learns from results across a whole league. Pitches with certain traits get more swings and misses, weaker contact, or more called strikes. When a new pitch shares those traits, it scores higher. Stuff+ ignores where the pitch was located and what happened on that specific pitch. That makes it useful with small samples, like a bullpen session, where stats like ERA or batting average tell you almost nothing.
Stuff+ also looks at context within a pitcher's arsenal. Most models compare each pitch with the pitcher's main fastball, so a changeup with a big gap in speed and movement scores better than one that looks like a slow fastball. Every company trains its own model on its own data, so a 110 from one provider may not equal a 110 from another. Compare scores from the same system.
Video explanation
Jake Fishman, PitchLab’s co-founder and CEO, pitched in the major leagues for the Miami Marlins. Here he explains Stuff+ and what it means for your pitching.
What affects Stuff+
Velocity
Faster pitches score higher when everything else is equal. Velocity is one of the biggest inputs for fastballs.
Movement
Induced vertical break and horizontal break define a pitch's shape. Unusual shapes, like a four-seamer with big ride or a sweeper with a lot of sweep, grade well.
Release height and extension
A low release with high ride, or long extension toward the plate, makes a pitch harder to hit. The model accounts for where the ball leaves the hand.
Spin rate and axis
Spin drives movement, and some models use spin rate and axis directly. Efficient spin that produces big movement helps the score.
Gap from the fastball
Offspeed pitches and breaking balls score better when they differ from the fastball in speed and movement. A changeup that looks like a slow fastball grades poorly.
What’s a good Stuff+?
| Pitch type | Average | Good | Great | Excellent |
|---|---|---|---|---|
| Four-seam fastball | 100 | 105 | 110 | 115+ |
| Sinker | 100 | 105 | 110 | 115+ |
| Slider / sweeper | 100 | 105 | 110 | 115+ |
| Curveball | 100 | 105 | 110 | 115+ |
| Changeup / splitter | 100 | 105 | 110 | 115+ |
Stuff+ is a model output, and each provider uses its own model and data, so compare scores only within one system. Some models set each pitch type's average at 100, while others use one league-wide average, which can make breaking balls score higher than changeups and sinkers.
How PitchLab measures it
PitchLab gives each tracked baseball pitch a Stuff+ score alongside its velocity, spin, and movement, so you can see which of your pitches grade best. Session trends show whether grip or mechanical changes are moving the score.
Stuff+ FAQs
How do you get a Stuff+ score with your phone?
Set an iPhone 12 or newer on a tripod about 2 ft behind the pitcher, facing home plate, and start a session in PitchLab. PitchLab gives each tracked baseball pitch a Stuff+ score from its velocity, spin, and movement.
Is there an app that calculates Stuff+?
Yes. PitchLab gives every tracked baseball pitch a Stuff+ score using just an iPhone, with no radar or tracking unit. PitchLab is free to start.
What’s the best app for improving Stuff+?
Look for an app that grades every pitch and shows the velocity, spin, and movement behind the score, so you know what to change. PitchLab shows Stuff+ next to all of those numbers and tracks it across sessions.
What does Stuff+ mean?
Stuff+ is a rating of a pitch's raw quality. It uses physical traits like velocity, movement, and release point, and it ignores results and location. A score of 100 is league average, and anything above 100 is better than average. The plus sign means it is scaled to a league norm, like OPS+ or ERA+.
How is Stuff+ calculated?
A machine learning model is trained on a large set of tracked pitches and their outcomes, like swings and misses and quality of contact. The model learns which mixes of velocity, movement, spin, and release lead to better results. It then scores any new pitch and scales the output so 100 equals league average.
What is a good Stuff+ score?
A score of 100 is average, 105 is good, 110 is great, and 115 or higher is excellent. Single pitches can score well above that, especially top sliders and sweepers. The same scale works for a pitcher's whole arsenal, where 110 or more is well above average.
What is the difference between Stuff+, Location+, and Pitching+?
Stuff+ grades only a pitch's physical traits. Location+ grades where pitches are thrown, based on the count and pitch type. Pitching+ combines stuff and location into one number. All three use 100 as league average.
