ERA
ERAEarned Run Average: earned runs allowed per nine innings; the headline pitching stat.
ERA is the number of earned runs a pitcher allows per nine innings: ERA = (earned runs / innings pitched) x 9. A 3.00 ERA means three earned runs every nine innings.
Only earned runs count. Runs that score because of errors or passed balls are unearned and excluded, so a pitcher isn't penalized for the defense behind them, which is why earned vs. unearned bookkeeping matters so much.
ERA is the standard measure of run prevention, though it depends on defense and the official scorer's error calls. It's usually read with WHIP for a fuller picture.
Bleacher Notes computes ERA from the earned-run reconstruction, so unearned runs from errors never inflate a pitcher's ERA.
How is ERA calculated?
Divide earned runs by innings pitched and multiply by nine. Only earned runs count; runs that scored on errors or passed balls are excluded.
What is a good ERA?
It varies by level, but below 3.00 is generally excellent and around 4.00 is average in many leagues.
Let the scorebook keep itself.
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