What is ERA in baseball?

Earned Run Average is the average number of earned runs a pitcher allows per nine innings. It is the classic measure of run prevention, calculated as earned runs times nine divided by innings pitched, so a lower ERA is better.

How do I enter partial innings?

Baseball counts innings in thirds. Enter one out as .1 and two outs as .2, so 6 and one-third innings is typed 6.1. The calculator converts these baseball-notation thirds into true decimals before computing ERA.

What is FIP and why compare it to ERA?

Fielding Independent Pitching estimates ERA using only outcomes a pitcher controls — strikeouts, walks, hit batters, and home runs — removing the effect of defence and luck. A FIP well below ERA suggests a pitcher was unlucky and may improve.

Why is the ERA multiplier nine?

ERA standardises to a full nine-inning game so pitchers with different workloads compare fairly. Multiplying earned runs by nine and dividing by innings pitched scales any sample up to a per-nine-innings rate.

What counts as an earned run?

An earned run is one the pitcher is held responsible for, excluding runs that scored only because of errors or passed balls. The official scorer decides which runs are earned, and only those go into the ERA calculation.

Baseball ERA Calculator

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Earned Run Average remains the headline statistic for evaluating pitchers. This calculator applies the official formula and, importantly, handles the baseball-specific way innings are written in thirds, so 6.1 means six and a third innings rather than 6.1 decimal innings. It also estimates FIP to reveal how much defence and luck shaped the raw ERA.

How it works

ERA scales earned runs to a nine-inning game after converting innings notation:

real IP = whole innings + (thirds digit / 3)   // .1 -> .333, .2 -> .667
ERA     = (ER × 9) / real IP

FIP isolates pitcher-controlled outcomes using the standard formula with a constant near 3.10 to put it on the ERA scale:

FIP = (13×HR + 3×(BB + HBP) − 2×K) / IP + 3.10

Example and tips

A pitcher with 18 earned runs over 50.2 innings pitched has a real IP of 50.667, so ERA = 18 × 9 / 50.667 ≈ 3.20. If that same pitcher struck out 55 and walked only 12, FIP would land lower, hinting the ERA could improve as luck normalises. Always enter innings in thirds notation (.1 or .2), never as plain decimals, or the result will be wrong.