Team Earned Run Average (ERA) is the number of earned runs a team gives up every nine innings, as measured by ((Earned Runs * 9) / Innings Pitched). Excluded from this calculation are unearned runs, which are runs that scored as a result of an error or a passed ball that, per the determination of the scorekeeper, would not have scored otherwise.
More about Team Earned Run Average
Overall Team ERA is fairly useful in determining the effectiveness of an entire pitching staff. It is also helpful to break out Team ERA by starters and relievers. It does not take into account luck as measured by the percentage of balls hit in play that fall for hits, and it does not take into account how many runs a team either allows or saves as a result of defensive play other than errors. For example, a team with a poor defensive left fielder will give up more hits to left field through no fault of the pitchers, even though those runs will count as earned. The left fielder would not be making any errors but would simply not be making as many plays.