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How Is ERA Calculated

ERA is calculated as a rate stat: earned runs are scaled to a full regulation game and then divided by IP.

Direct answer

The calculation is earned runs multiplied by game length, divided by IP. A lower result means the pitcher allows fewer earned runs per full game.

Why IP matters

IP makes the stat comparable. Without workload context, a pitcher who allowed 2 earned runs across a short outing would look the same as one who carried a much longer appearance.

Partial outs

One extra out is one-third of an inning. Two extra outs are two-thirds of an inning. That conversion should happen before the final calculation.

Use the tool

For a quick answer, open the ERA calculator and enter earned runs, IP, extra outs, and game length.