Fun with batting average

When writing about Mark Reynolds yesterday, I noticed myself talking about what would happen to his batting average—in exact terms—should different components change. I’ve been using a simple Excel spreadsheet to determine this for a while now, but I realized that I’ve never shared it with you guys.

I wrote a little about it at MLB Front Office on Wednesday and put up a file for download. The one I’m posting here is a little bit more complex. This one incorporates home run per flyball rate (HR/FB) and flyball rate (FB%).

It works pretty simply. First, take a look at the layout:


Pretty intuitive. The only fields you need to fill in are AB, Contact Rate, HR/FB, FB%, and BABIP. Everything else gets calculated for you automatically. Think Mark Teixeira deserved a .300 BABIP? Change it, and the batting average adjusts itself to .274.

If you haven’t been hanging around here long enough to understand why these stats are important in determining batting average, I’ll give you the quick crash course.

Contact rate – Contact rate is measured by (AB-K)/AB. It measures how often the ball is contacted, how often the hitter doesn’t strike out. Logically, the only way a ball can possibly turn into a hit is if the batter makes contact. If he strikes out, it is not possible for him to reach base via hit. Contact rate remains pretty stable from year-to-year.

BABIP – Stands for Batting Average on Balls in Play, measured by (H-HR)/(AB-HR-K). BABIP measures the rate that balls put into the field of play fall for hits. BABIP is prone to fluctuations, sometimes quite large, and often due to random luck.

Home Runs – Home runs make up the remaining portion of hits, hits on contact balls that don’t fall into the field of play, but rather clear the fences and are—essentially— ndefensible. Home runs are broken down into two stats.

Flyball rate – The percentage of contacted balls that are fly balls. Used in conjunction with HR/FB (and AB) to calculate the raw number of home runs. Only balls that are hit in the air can become home runs, which is why we use fly ball rate. Line drives can be home runs too, but very few do (in 2007, just 3.5 percent of all home runs were line drives). Flyball rate is somewhat stable from year-to-year and is a definitive skill.

HR/FB – Home run per flyball rate. Simply measures how many fly balls it takes for a batter to hit a home run. A definitive skill and more skill related than BABIP, but we do sometimes see some regression to the mean.

Note: I prefer to use outfield flyball rate and home runs per outfield fly ball. I think excluding infield flies (i.e. popups) is good practice because these balls have zero chance of becoming home runs and aren’t indicative of good power, which is really what we are trying to show. Either one will work in this calculator as long as you stay consistent. The example currently in the calculator includes infield flies.

Concluding thoughts

Nothing revolutionary, but I think this will make these types of calculations a lot easier and quicker. Also, if you’ve struggled to understand how the three elements of batting average (contact rate, BABIP, and home run rate) interact, fooling around a little with this should help clarify it for you.

Hopefully, throughout the year, as we see certain players putting up lucky or unlucky numbers (maybe BABIP or HR/FB or, early on, FB%), we’ll be able to use this to quickly find out what we should expect them to hit going forward, taking the adjustment into account. Or you can just have fun fooling around with it, trying different combinations!

If you have any questions, feel free to let me know!

Download the calculator

Download the calculator!

A Hardball Times Update
Goodbye for now.

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