Formula and method
ERA = 9 × earned runs ÷ (complete innings + additional outs ÷ 3).
Worked example
For 2 earned runs in 6 complete innings, ERA = 9 × 2 ÷ 6 = 3.00. With one additional out, true innings are 6⅓ and ERA = 18 ÷ 6⅓ ≈ 2.84.
What the result means
ERA expresses earned runs allowed per nine innings pitched. It is a rate, not a prediction of a future game.
Common input mistakes
- Reading scorebook 6.1 as 6.1 decimal innings. It means six innings plus one out.
- Entering total runs instead of earned runs.
- Calculating with zero recorded outs.
Scope and limitations
This calculator does not decide which runs are earned. It uses the earned-run count you supply and the nine-inning convention; it does not apply to formats that use a different game length.
This is a deterministic calculation aid, not a player evaluation, prediction, fantasy recommendation, or betting tool. No live statistics are fetched.
Privacy
Entered statistics are calculated in this browser tab. This tool has no account, input submission, URL state, or persistent storage for your entries.