Baseball By the Numbers - How To

Figuring a pitcher’s Earned Run Average (ERA):

According to the official rules of baseball, an earned run is a run for which the pitcher is held accountable. The pitcher is charged with an earned run for every base runner that scores who hasn’t reached base because of an error. In more basic terms, the pitcher is responsible for runs scored as a result of:

Hits Sacrifice bunts Sacrifice flies Stolen bases Putouts Fielder’s Choices Bases on balls thrown by the pitcher Batters hit by the pitcher Balks by the pitcher Wild pitches thrown by the pitcher

The earned run average is the average number of earned runs scored on a pitcher per game. A quick glance at the formula involved in determining a pitcher’s ERA can be a bit scary — reminiscent at times of the complex formulas used to determine how much rocket fuel is needed to get the Space Shuttle to lift off — but it’s really not that difficult at all.

A pitcher’s ERA is calculated by taking the number of earned runs scored on the pitcher and dividing it by one-ninth the total number of innings pitched. The formula, itself, is as follows:

ERA = Earned runs/(innings pitched/9)

For example, say the pitcher gives up five earned runs in seven innings of work. The formula would look like this: ERA = 5/(7/9) multiplying out to an ERA of 6.42. Make sense?

So what constitutes a strong ERA, and how can you tell if the guy hurling for your team should strike fear into opposing batters or his own manager? In 1999, Boston Red Sox pitcher Pedro Martinez led the American League with an ERA of 2.07. For every nine innings he pitched, he allowed just over two earned runs. Conversely, former Tampa Bay pitcher (and now Cleveland Indians farmhand) Bobby Witt had an ERA of 5.84. He allowed nearly six runs for every nine innings he pitched.

Figuring Slugging Percentage:

Slugging Percentage is a mathematical equation. A homerun is four points, triple 3 points, a double is two, and a single is one (a point is a base reached safely). Take the number of points added up, then divide by the number of at bats. For example, a batter goes 1 for 4 and hits a home run, which is four points. Four points divided into 4 at bats equals 1.000 slugging percentage.

Figuring Batting Average:

Divide number of hits by the number of at bats (at bats does not count walks+hit by pitch+catchers inferference+sacrifices).

Figuring On Base Percentage (OBP):

This ratio takes into account a player’s (a) hits, (b) times he reached base by walk; and (c) times getting hit by a pitch. Some say this average is more indicative of a batter’s total value as a hitter because it factors in every time that a hitter reaches base safely, not just the time the batter gets a hit.

(a) Add Hits + Walks + Times Hit by Pitch (This sum is the total Times on Base)

(b) Calculate Total Plate Appearances by adding At Bats (AB), Walks (BB) and times Hit by Pitch (HBP)

(b) Then divide sum A (Times on Base) into Sum B (Total Plate Appearances)

Figuring On Base Percentage plus Slugging Percentage (OPS):

(a) Calculate the player’s On-Base Percentage;

(b) Calculate the player’s Slugging Percentage.

Figuring Fielding Percentage:

Add up a fielder’s assists, putouts, and errors (this is called ‘total chances’). Then add up a fielder’s putouts and assists and divide that by the number of total chances.

Example: A player has 150 assists, 95 putouts, and 5 errors. The player has 250 total chances (150+95+5=250). Add up the putouts and assists (150+95=245) and divide by the total chances (245 divided by 250 = .980). The player’s fielding percentage is .980.

Sources:

http://www.buzzle.com/
http://wiki.answers.com/

Last 5 posts in Spring Training

Approaching the Plate - November 19th, 2008
Baseball Tips for Pitchers - Pitching Easy - November 18th, 2008
Mechanics of a Fast Ball - August 4th, 2008
Baseball Glossary of Terms - June 29th, 2008
Video: How to Pitch From the Wind-up - June 28th, 2008

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