Calculating Earned Run Average in Baseball - Free Math Help



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** Earned Run Average **

A major league pitcher is often judged on the basis of his earned run
average, or ERA. This number represents the average number of earned runs
given up by the pitcher per nine innings.

An *earned run* is any run that the opponent scores off a particular
pitcher except for runs scored as a result of errors. For instance, if Tim
Lincecum gives up three solo homeruns, and then an error causes another run
to score, he is only credited with those first three runs that were "his

The earned run average can be calculated using the following formula:

-(Earned Runs/Innings Pitched) x 9-

Therefore, if Roy Halladay is charged with 19 earned runs in his first 89
innings pitched, his ERA would be 19 divided by 89, which is .2135, times
9, which is 1.92, a very good number.

(19 runs / 89 innings) x 9 = 1.92

Don't forget the 9 at the end. By calculating runs/innings you have only
figured out earned runs per inning, but you must keep in mind that an ERA
is actually earned runs per nine innings, since a regulation game is 9
innings. The number, usually represented with two places after the decimal,
shows how many runs the pitcher gives up in an average complete game.

Here's one last example: Johan Santana yielded 66 earned runs over 234.33
innings in 2008. What is his ERA? Simple -- divide 66 runs by 234.33
innings and multiply by 9. The correct answer is 2.53.

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how is era calculated

Earned run average - Wikipedia, the free encyclopedia


** Earned run average **

From Wikipedia, the free encyclopedia
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This article *possibly contains original research*. Please improve it by
verifying the claims made and adding inline citations. Statements
consisting only of original research may be removed. /(November 2010)/

The lowest career ERA is 1.82, set by Chicago White Sox pitcher Ed Walsh.

In baseball statistics, *earned run average* (*ERA*) is the mean of earned
runs given up by a pitcher per nine innings pitched. It is determined by
dividing the number of earned runs allowed by the number of innings pitched
and multiplying by nine. Runs resulting from defensive errors (including
pitchers' defensive errors) are recorded as unearned runs and are not used
to determine ERA.


· 1 Origins
· 2 ERA in different decades and baseball eras

· 2.1 Infinite and undefined

· 3 Other external factors

· 3.1 Starters and relievers
· 3.2 DH rule
· 3.3 Location

· 4 Sabermetric treatment of ERA
· 5 All-time career leaders

· 5.1 Career leaders in the live-ball era (post-1920)

· 6 See also
· 7 References


\mathrm{ERA} = 9 \times

Henry Chadwick is credited with first devising the statistic, which caught
on as a measure of pitching effectiveness after relief pitching came into
vogue in the 1900s. Prior to 1900 – and, in fact, for many years
afterward – pitchers were routinely expected to pitch a complete game,
and their win-loss record was considered sufficient in determining their

Some criterion was needed to capture the apportionment of earned-run
responsibility for a pitcher in games that saw contributions from other
pitchers for the same team. Since pitchers have primary responsibility to
put opposing batters out, they


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