ERA Calculator
Calculate a pitcher's earned run average from earned runs and innings pitched — ERA = (earned runs ÷ innings pitched) × 9, rounded to two decimal places.
Input
Output
ERA equals (earned runs ÷ innings pitched) × 9.
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/era-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"earnedRuns": "27",
"inningsPitched": "90"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `era-calculator` tool (ERA Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/era-calculator/"
width="100%" height="520" frameborder="0" scrolling="no" loading="lazy"
title="ERA Calculator — iotools.cloud"
sandbox="allow-scripts allow-forms allow-same-origin allow-downloads allow-popups allow-popups-to-escape-sandbox"
allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
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Guides
The ERA Calculator works out a pitcher's earned run average — the single most common way to measure pitching effectiveness in baseball and softball. Enter the number of earned runs a pitcher has allowed and the number of innings pitched, and the tool returns the ERA instantly, rounded to the standard two decimal places.
ERA answers a simple question: on average, how many earned runs would this pitcher give up over a full nine-inning game? A lower number is better. Elite starters typically sit under 3.00, while an ERA above 5.00 usually signals a rough stretch.
How to use it
- Enter Earned runs — the runs charged to the pitcher that were not the result of a fielding error or passed ball.
- Enter Innings pitched — the total innings the pitcher has thrown. Partial innings are entered as decimals (see the note on baseball notation below).
- Read the Earned run average (ERA) result. It updates automatically as you type, and you can copy it with one click.
The formula is:
ERA = (Earned Runs ÷ Innings Pitched) × 9
For example, a pitcher who allows 27 earned runs across 90 innings has an ERA of (27 ÷ 90) × 9 = 2.70.
What counts as an earned run?
An earned run is any run a pitcher gives up without the help of an error or a passed ball by the defense. Runs that score only because of a defensive miscue are unearned and do not count toward ERA. Because of this, ERA isolates the pitcher's own performance from the fielding behind them.
How do I enter partial innings?
In official box scores, fractional innings are written using a baseball convention: .1 means one out (one-third of an inning) and .2 means two outs (two-thirds). This calculator treats the innings-pitched value as a plain decimal, so if you are copying from a box score, convert first: 6 and 1/3 innings is 6.33, and 6 and 2/3 innings is 6.67. A whole number like 90 needs no conversion.
Is a lower ERA always better?
Yes — ERA measures runs allowed, so fewer is better. Keep in mind that ERA depends on sample size. One bad start early in a season can inflate the number dramatically, while a full season of innings gives a much more stable reading. Compare ERAs over similar innings totals for a fair picture.
Does this work for softball?
The formula is identical, but softball is typically a seven-inning game, so many leagues multiply by 7 instead of 9 for their earned run average. This tool uses the standard nine-inning baseball convention. For a seven-inning softball ERA, you can adjust the result by multiplying by 7/9.
Privacy
This calculator runs entirely in your browser. The earned runs and innings you enter are never sent to a server, stored, or logged — the math happens locally on your device.