Can someone tell me how exactly ERA is calculated? Is it the total number of pitches or just batters? And do those batters need to be on base to count against a pitcher’s ERA?

(Earned runs) * 9 / innings pitched.

So, for example, if Kerry Wood this season has given up 4 runs and has pitched 17 innings, then his ERA is (4*9)/17, or 36/17, or 2.18.

DISCLAIMER: These are not Kerry Wood’s actual stats for this season, AFAIK.

ERA only counts runs that cross home plate and they only count as earned runs <ie if a runner is on base from an error on shortstop it does not count against the pitchers ERA>. Also if a pitcher “inherits” runners from a previous pitcher those runs, IF they score, go on the ERA of the previous pitcher. Its based on a 9 inning game. If a pitcher gives up say 1 home run in 1 inning his ERA is a 9. This figure supposes that you will allow 1 run per inning for 9 innings hence an ERA of 9. If you pitch a whole game and give up 3 runs…<no errors from other teammates etc> Then your ERA is obviously a 3.0

HeyHomie- dig- if Kerry pitches through two outs, does he get partial credit for that inning? Along the same lines, if he has a few runs scored on him in said inning, do they count?

Also, each out that occurs while that pitcher is pitching is counted as one third of an inning pitched. Runners that reached base when the previous pitcher was still pitching but scored after the pitching change may or may not count toward that new pitcher’s ERA, based on some complex rules I no longer remember. There are complex rules for when one batter gets pitches from more than one pitcher; the runs attributed to that batter will be assigned to one pitcher or the other depending on the count when the pitcher change occured.

See Rule 10.18 of the MLB’s Official Rules for the grostesque details, if you want.

Yum, baseball rules.

Hell if I know. I was stretching the depths of my knowledge just coming up with the ERA formula.

Sheesh.

**stolichnaya**, if the pitcher puts out two batters, then he gets credit for two-thirds of an inning pitched. Runs scored by batters who reached base while that pitcher was pitching count as earned runs – unless the batter reached base, advanced, or scored on an error.

slight hijack question…if the PITCHER makes a fielding error or a batter is HBP does the runner count vs pitchers ERA if he eventually scores?

This statement isn’t quite accurate on several points. Responsibility for a runner who scores is assigned to the pitcher who allowed him to reach base to begin with. It doesn’t matter who is actually pitching when he scores. Also, the method to determine whether a run is earned is to hypothesize what would have happened if the error had not occured but the rest of the inning was unchanged. Any runs that wouldn’t have been scored *in that inning* had the error not been committed are unearned. For example, imagine that the first batter in an inning reaches on an error. If the pitcher gets the next two batters out, then the inning should be over, but it’s not over because of the error. Any runs scored in the rest of that inning are unearned, even if they’re the result of legitimate hits.

There’s one extra little wrinkle to that rule: If a new pitcher enters the game, his stats are computed without regard to what transpired before he entered. So, it’s not unusual to see a situation in which runs are earned as far as the pitcher is concerned but unearned for the team.

As far as counting innings pitched, if you’re on the mound when an out is made, you get credit for [sup]1[/sup]/[sub]3[/sub] inning pitched. It’s theoretically possible to enter a game and pick inherited runners off base and get credit for innings pitched without ever throwing a pitch.

If you think that what I just said is incomprehensible, check out Rule 10.18 for the official word.

From Rule 10.18:

So the answers to your questions are no (pitcher’s error) and yes (batter hit by pitch).

Here’s a good one. Suppose a pitcher comes into the game with no one on and two outs when, thanks to an error, there should have already been three outs. Now supposed he gets hammered and isn’t pulled from the game until after he’s thoroughly ensured his opponent’s future by allowing them to score five or six runs without getting a single one of them out. Do those runs count as earned or are they unearned because the inning should have been over by the time he got out there?

**braintree**, those runs will be earned for the pitcher (except that any runners who were already on base when he entered are not charged to him, but your hypothetical assumes nobody on), but unearned for the team and for the pitcher he relieved, for the reason **Mandarax** explained above. Errors affect whether the runs are earned for the pitcher only if they take place after the pitcher enters the game.