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Earned run average
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<p>In <a href="/facts/Baseball_statistics/jX18gq0B">baseball statistics</a>, earned run average (ERA) is the average of <a href="/facts/Earned_run/rkT4D7Rp">earned runs</a> allowed by a <a href="/facts/Pitcher/08gAFpa3">pitcher</a> per nine <a href="/facts/Innings_pitched/q4AVyC6m">innings pitched</a> (i.e. the traditional length of a game). It is determined by dividing the number of earned runs allowed by the number of innings pitched and multiplying by nine. Thus, a lower ERA is better. Runs resulting from <a href="/facts/Passed_ball/dvkojHfY">passed balls</a>, <a href="/facts/Error_(baseball)/YGrIxenw">defensive errors</a> (including pitchers' defensive errors), and runners placed on base at the start of extra innings are recorded as <a href="/facts/Unearned_run/rkT4D7Rp">unearned runs</a> and omitted from ERA calculations. </p>