ERA Calculator
ERA (earned run average) is the classic measure of a pitcher's effectiveness: how many earned runs they'd allow over 9 innings. Enter earned runs and innings pitched — the calculator understands baseball's .1 / .2 innings notation (5.1 means 5⅓ innings). Runs entirely in your browser.
Frequently Asked Questions
What is ERA in baseball?
ERA stands for earned run average: the number of earned runs a pitcher allows per nine innings pitched. It's the standard one-number summary of pitching performance — lower is better. The formula is simple: ERA = (earned runs × 9) ÷ innings pitched.
What is a good ERA?
In modern MLB, an ERA under 3.00 is excellent (often Cy Young territory), 3.00–3.75 is very good, 3.75–4.50 is roughly league average, and anything above 5.00 is a problem. Context matters: the league-average ERA moves with the run environment, so a 4.00 ERA in a high-scoring year can be above average.
What do 5.1 and 5.2 innings mean?
Baseball uses its own notation for partial innings: .1 means one out (⅓ of an inning) and .2 means two outs (⅔ of an inning). So 5.1 innings is really 5⅓ innings, and 5.2 is 5⅔. The decimal .3 doesn't exist in this notation — after 5.2 comes a full 6.0. This calculator converts the notation automatically.
What's the difference between earned and unearned runs?
Earned runs are runs that scored without the help of a fielding error or passed ball — they're "charged" to the pitcher. If a runner reaches on an error and later scores, that run is unearned and doesn't count against the pitcher's ERA. The official scorer makes the call on every play.
Can ERA be 0.00?
Yes — any pitcher who hasn't allowed an earned run has a 0.00 ERA, no matter how many innings they've thrown. A 0.00 ERA over a full season as a starter is essentially impossible in the modern game; the single-season record for a qualified starter is 1.12, set by Bob Gibson in 1968.
Is ERA or WHIP a better stat?
They measure different things. ERA measures runs allowed (the bottom line), while WHIP (walks + hits per inning pitched) measures baserunners allowed and is less influenced by sequencing luck and defense. Most analysts look at both, plus strikeout and walk rates, for a full picture of a pitcher.