ERA Calculator
Calculate a pitcher's Earned Run Average from earned runs and innings pitched.
Use .1 for one out, .2 for two outs.
Earned Run Average, or ERA, is baseball's classic measure of a pitcher's effectiveness: the number of earned runs they give up per full game. This calculator works it out from the earned runs allowed, the innings pitched, and the game length, and it handles fractional innings the way the box score does. Enter the numbers and the ERA appears instantly, all in your browser.
The ERA formula
ERA scales a pitcher's earned runs up to a full game's worth of innings:
ERA = (Earned Runs × Game Length) ÷ Innings Pitched
Game length is normally 9 innings, so a pitcher who allows 3 earned runs over 6 innings has an ERA of (3 × 9) ÷ 6 = 4.50. The calculator lets you change the game length for softball or other formats that use 7 innings. Crucially, it converts the fractional innings pitchers record — where ".1" means one out (a third of an inning) and ".2" means two outs — into the correct decimals before dividing, which a plain calculator would get wrong.
Reading fractional innings correctly
The most common ERA mistake is treating "5.2 innings" as five and two-tenths. In baseball it means five innings plus two outs, or 5.667 innings, because each out is a third of an inning. This tool asks for the whole innings and the extra outs separately, then does that conversion for you. A lower ERA is better, and the figure is most meaningful over a decent number of innings — a single rough outing can spike an ERA that a full season would smooth out.
Frequently Asked Questions
What counts as an earned run?
An earned run is one charged to the pitcher that scored without the help of a fielding error or passed ball. Runs that only scored because of a defensive miscue are "unearned" and are excluded from ERA.
How do I enter innings like "5.2"?
Enter the whole innings and the extra outs separately. "5.2" means five innings and two outs — the tool converts those two outs to two-thirds of an inning so the maths comes out right.
Why can I change the game length?
Because not every format plays nine innings. Setting it to 7, for example, gives a correct ERA for softball or seven-inning games, since the formula scales runs to a full game.
Is anything I enter stored?
No. The calculation runs in your browser and nothing is uploaded or saved.