# Bauer Units and Pitch Comparison

In our article Spin Rate Part 1, we formally introduced Bauer Units. Bauer Units normalize spin rate per velocity, which, as you’ll see, is important when comparing pitchers’ spin rates.

Let’s review the Bauer Unit equation:

Bauer Units = Spin Rate (RPM) / Velocity (MPH)

This is pretty straight forward. However, up until now we haven’t shown the best ways that you can use it, so let’s explore those possibilities.

# Bauer Units and MLB

Let’s have some fun with some MLB numbers. The easiest way to access velocity and spin-rate data is through Baseball Savant. The general idea when discussing fastball spin rate is that the MLB average is a 92 mph fastball spinning at 2200 rpm. This makes the average Bauer Unit 23.9, which can be rounded to 24.

So, let’s try to answer three simple questions when looking at fastballs:

- Do most high-spin pitchers have above-average spin rate by Bauer Units?
- Do most pitchers with fastest velocities have above-average spin rate by Bauer Units?
- Do Bauer Units allow us to compare pitches differently than by spin rate alone?

On Baseball Savant we looked at four-seam fastballs and set a low qualification of a 100-pitch- minimum and 100 results. So, we’re looking at both relievers and starters.

*Answer to Question 1: *Yes. If we look at the top 20 pitchers by spin rate, every one of them has Bauer Units that are above the league average. The lowest velocity pitcher of the group was Xavier Cedeno, at 88.5 mph, while every other pitcher was above 92 mph. This suggests that if you have a high spin rate, it’s likely that you have high Bauer Units.

*Answer to Question 2: *No. Looking at the 20 highest average velocities, we see that pitchers who throw harder definitely ** do not** automatically have higher Bauer Units. The top 20 is an even split: 10 pitchers have above average Bauer Units while 10 are below average.

This can help clear up some confusion when you are looking at pitchers who throw high 90s with spin rates in the 2300 range. Technically 2300 rpm is above the average of 2200, but with velocity taken into account, they are actually below average. Mauricio Cabrera, Carlos Estevez, and Arquimedes Caminero are good examples of this.

*Answer to Question 3: *Bauer Units seem to be best used when comparing pitchers’ spin rates at different velocities. This is most obvious in the velocity chart, and it becomes more apparent as you look very different velocities.

You can see two drastic differences by comparing Ken Giles and Marco Estrada, who both averaged 2403 rpms on their fastballs last year.

Giles has a just above average Bauer Unit, while Estrada has a very high Bauer Unit, it’s velocity that makes the difference.

Now, I know you’re thinking this is great and all, but how does it help me?

# Bauer Units and Pitch Comparison

Bauer Units let younger players better understand what their spin rates for fastballs mean, even at lower velocities. It frankly doesn’t mean much to anyone that a high school athlete may be throwing at 78 mph at 1800 rpm. But, it does matter once you look at the Bauer Units.

We can get a pretty good idea of where a pitcher stands by using a device like Rapsodo, even if he throws at velocities that aren’t directly comparable to MLB pitchers.

Taking this as a snapshot will at least give a player and coach an understanding of where a pitcher’s fastballs stands and how his fastball can be used most effectively.

League average Bauer Units -> look into developing a 2-seam

Above average Bauer Units -> try to throw middle/up in the zone

Below average Bauer Units -> try to throw middle/down in the zone

Now what we don’t understand is exactly how spin rate changes as players age (and grow), but regular check-ins will be able to account for that.

Bauer Units can be used to compare offspeed pitches as well, but unlike with fastballs, they don’t give us as much information on how to use a pitch or its effectiveness.

Bauer Units, in this instance, can only be used to compare the total spin. But again, because of the complexity of spin rate, its relation to spin axis, and velocity, it won’t be able to tell us how much a pitch moves or how effective it is.

However, Bauer Units are still an interesting statistic that is simple to calculate in order to compare pitchers to one another—especially since the velocity of offspeed pitches varies more than fastball velocity.

# Conclusion

So we’ve seen that having a high spin rate in Major League Baseball usually means that a pitcher also has high Bauer Units. But pitchers who throw at higher velocities can have drastically difference Bauer Units. This suggests that using Bauer Units gives us a better way to compare pitchers’ fastball spin rates.

For pitch development, Bauer Units can help determine how a younger pitcher can best use his fastball. They are interesting to know for offspeed pitches, but knowing an offspeed pitcher’s Bauer Unit doesn’t directly benefit pitch development.

In the end, Bauer Units are going to be most useful for coaches who deal with pitchers who don’t throw at elite velocities, such as high school and some college pitchers. It will normalize spin rate so you can understand if your pitchers have an average, above average, or below average spin rate, which will affect how your pitchers can utilize their fastballs.

A goal for us this summer is to investigate offspeed pitches and the relationship between velocity and *useful spin*, a metric that we can get with Rapsodo. We’ll let you know what we find!

*This article was written by Associate Researcher Michael O’Connell*

**Check out what else we know about everything spin rate / pitch design here:**

Interesting. So in the conclusion of your article about being “more” useful to college and high school….does average Bauers stay consistent at all levels? Or does it get lower (assumption) and an avg pro Bauer spin might be an above average high school bauer spin?

Not sure! The only public data that is available right now is for MLB. I wouldn’t be surprised to see differences but we just don’t have enough information right now.

Hopefully we can collect some data on different ages and start to figure this out.

[…] on spin rates and spin axis of each athlete’s pitches. Another useful metric has been the Bauer Unit. This metric lets us break down each pitch’s spin and how it forecasts at higher velocities as […]

[…] our original piece on Bauer units, we said that the MLB league average for a four-seam fastball was 23.9, which, for simplicity sake, […]

[…] further reading https://www.drivelinebaseball.com/2017/03/bauer-units-pitch-comparison/ BU = Spin Rate (RPM)/Velocity […]

Contemporary baseball analysis has found no correlation between baseball velocity and spin rate when it comes to curveballs specifically. That said, the average curveball at ~60 mph in 2017 spun at roughly 1800 rpm. While it is possible, it would be rare to find a 60 mph curveball spinning at 2500 rpm.

You list that someone above league average in spin rate should be middle/up in zone. If you look at heat maps on fan graphs, aren’t fastball high spin rate guys usually more successful anywhere in the strike zone? I found it difficult to find a correlation with those guys being strictly up in the zone.

In your comparing bauer units among top 20 pitchers graph, what do the results represent?

That there are differences if you are sorting by velocity or spin rate, from highest to lowest. You can see in the ‘Bauer Units’ column that the results don’t match up perfectly with either velocity or spin rate. So it’s more useful to sort by Bauer Units than either velocity or spin rate alone. Then you should look at the ball axis.