ERA Calculator

A pitcher's earned run average (ERA) is the single most quoted measure of pitching effectiveness. It answers a simple question: if this pitcher threw a full nine-inning game at their current rate, how many earned runs would they give up? This calculator takes the earned runs you've allowed and the innings you've pitched and converts them into that standardized per-nine figure so you can compare any pitcher regardless of how much they've thrown.

The ERA Formula

ERA scales earned runs to a nine-inning baseline. An earned run is a run that scored without the help of an error or passed ball — runs the pitcher is fully responsible for.

Innings pitched use baseball's thirds notation: a ".1" means one out (one-third of an inning) and ".2" means two outs. So 90.2 innings is 90 and two-thirds innings.

Worked Example

Suppose a pitcher has allowed 30 earned runs over 90 innings:

• Multiply earned runs by 9: 30 × 9 = 270
• Divide by innings pitched: 270 / 90 = 3.00 ERA

That 3.00 means the pitcher averages three earned runs per nine innings — a solid, above-average mark.

What's a Good ERA?

League-average ERA drifts with the era of baseball — it sat near 4.50 in high-offense seasons and below 3.50 in pitching-dominated ones. Always read an ERA against its league and ballpark context.

Earned vs Unearned Runs

The word "earned" is doing heavy lifting in ERA. A run is unearned — and excluded from ERA — when it scores only because of a defensive error or passed ball that should have ended the inning. The official scorer reconstructs the inning as if it had been played errorlessly to decide which runs would still have scored. This protects pitchers from being penalized for their fielders' mistakes, but it also means ERA carries a layer of subjective judgment.

Starters vs Relievers

Read ERA with the pitcher's role in mind. Relievers throw short, high-intensity bursts and often post lower ERAs than starters, who must pace themselves and face the same lineup multiple times. Comparing a closer's 2.20 ERA to a starter's 3.40 without that context can be misleading.

Strengths and Limits

ERA is intuitive and historically comparable, but it depends on the official scorer's judgment of what counts as an error, and it credits a pitcher's defense and bullpen. Modern analysts pair it with FIP and WHIP to separate a pitcher's own contribution from the fielders behind them.

Note: This calculator is for informational and educational use. Official statistics may differ slightly due to scoring decisions and inherited-runner rules.