ERA in Non-regulation length games

Question
In our American Legion season, teams play a 7 inning and 5 inning
double header.  Are you aware of a way to calculate ERA based on
batters faced instead of using the traditional formula (since this
formula is based on 9 inning games).

Answer
John,

All ERA is is a calculation of the average number of runs a pitcher gives up per 9 innings pitched.  The formula can be changed to give the average per 5 innings, 7 innings or whatever.  However, since we are all programmed to see ERA in its current form, using a different number of innings may trick our brains into thinking the pitcher is better then we think.

You could calculate the number of runs scored divided by the number of batters faced, which would tell you how many runs you give up per batter faced (with the worst being 1.000 and the best being 0.000) but again it isn't a statistic we are programmed to see, so we don't know what is good.  Is .5 good?  Is .1 good?  Wouldn't really know without some baseline.

Also, since complete games are rare in today's major leagues, ERA doesn't really work like it did way back when.  Back then, if a pitcher's ERA was 3.00, you expected that an average game would have him give up three runs.  Now, since so few pitchers throw complete games, you don't know how many innings he'll pitch.  But the formula still gives you a rating of how effective the pitcher has been this season.

I'd stick to the regular ERA formula.

Hope this helps!

Brian