ERA Calculator — Baseball Innings Notation
Calculate nine-inning earned run average from earned runs and baseball innings notation, correctly interpreting .1 and .2 as outs.
Calculate earned run average on the standard nine-inning baseball scale. Enter earned runs and the familiar innings notation from a pitching line. The calculator converts the innings to a whole number of outs first, preventing the common mistake of treating 6.2 innings as the decimal number 6.2.
How to use this tool
- Enter earned runs charged by the scorer.
- Enter innings as a whole number, or append .1 or .2 for the remaining outs.
- Check the recorded-out total and read the displayed rate.
Formula
Outs = 3 × whole innings + remaining outs; ERA = 27 × ER / outs
There are three outs per inning, so multiplying by nine innings is equivalent to multiplying earned runs by 27 and dividing by outs. A score line with no recorded outs has no finite denominator.
Example
The 2026 MLB rulebook gives 3 earned runs in 9⅓ innings. Enter 9.1, which is 28 outs. The exact calculation is 81/28 = 2.892857…, displayed as 2.89.
Frequently asked questions
What does the digit after the dot mean?
It is the number of outs after the whole innings: .1 is one-third and .2 is two-thirds. Values such as .3, .5 or .20 are rejected to avoid mixing notation systems.
Are all runs allowed earned runs?
No. Use the official scorer’s earned-run total. This calculator does not reconstruct error sequences or determine responsibility for inherited runners.
Can I average rates from separate appearances?
Combine the underlying counts and recorded outs first. Giving a one-out appearance the same weight as a complete game would distort the combined rate.
Sources
Last updated: 2026