ERA Calculator

About the ERA Calculator

Earned run average, or ERA, is the best-known statistic for judging a pitcher. It answers a simple question: how many runs, on average, would this pitcher allow over a full nine-inning game, counting only the runs that were their responsibility? A low ERA marks a pitcher who keeps opponents off the scoreboard; a high one, a pitcher who is being hit hard.

This ERA calculator works out a pitcher's earned run average from earned runs and innings pitched, handling the thirds-of-an-inning notation used in box scores. It works for nine-inning baseball or seven-inning softball and high-school games, and if you enter walks and hits allowed, it also gives WHIP.

How to Use the ERA Calculator

Enter the number of earned runs.

Enter the innings pitched, using .1 for one out and .2 for two outs: 6.2 means six innings and two outs.

Choose the number of innings in a game: nine for baseball, seven for most softball and high-school games.

Optionally, enter the walks and hits allowed to see WHIP.

How ERA Is Worked Out

Step-by-Step Example

50 earned runs in 180 innings, with 40 walks and 150 hits.

  ERA:    50 × 9 ÷ 180                    =  2.50
  WHIP:   (40 + 150) ÷ 180                =  1.06

45 earned runs in 162.1 innings.

  Innings:  162 + 1 ÷ 3                   =  162.333
  ERA:      45 × 9 ÷ 162.333              =  2.49

A softball pitcher: 10 earned runs in 35 innings.

  ERA:    10 × 7 ÷ 35                     =  2.00

Innings in Thirds

Earned and Unearned Runs

Not every run counts against the pitcher. The official scorer decides whether each run is earned. A run is unearned if it scored because of a fielding error or a passed ball, or if it would not have scored had the defence made a play it should have made. Only earned runs count towards ERA. Total runs allowed, including unearned runs, are sometimes shown as RA or RA9 for comparison.

What Is a Good ERA?

League averages change from season to season and between leagues, and ballparks matter: pitchers in hitter-friendly parks allow more runs. Relief pitchers often have lower ERAs than starters, because they face batters for only an inning or two. Adjusted statistics such as ERA+ compare a pitcher with the league average and account for the ballpark.

WHIP

WHIP — walks plus hits per inning pitched — measures how many batters reach base against a pitcher. It does not depend on what happens after a runner reaches base, so it is less affected by luck and defence than ERA. A WHIP around 1.00 is excellent, 1.20 to 1.30 is roughly average, and 1.50 or more is poor.

Small Samples

ERA can swing wildly over a few innings. A reliever who gives up three earned runs in one inning has an ERA of 27.00 for that game. Over a full season of 150 or more innings, ERA settles and becomes far more meaningful.

ERA for Relievers and Starters

Starting pitchers usually throw five to seven innings a game and 150 to 200 innings a season, so their ERA reflects a large sample. Relievers pitch an inning or two at a time and 50 to 80 innings a season, so a single bad outing can change their ERA noticeably. When comparing relievers, many analysts also look at strikeouts, walks and inherited runners who scored, because a reliever who enters with runners on base is not charged if those runners score — the earlier pitcher is.

Converting Between Game Lengths

To compare a seven-inning ERA with a nine-inning one, multiply by 9 ÷ 7: a 2.00 softball ERA is equivalent to about 2.57 over nine innings. The underlying rate — earned runs per inning — is the same, only expressed over a different game length.

Keeping Accurate Records

For youth and amateur teams, the hardest part is often recording innings correctly when pitchers change mid-inning. Record the outs each pitcher gets, then convert: every three outs is one inning, and a leftover one or two outs become .1 or .2.

Understanding Your Result

ERA is the earned run average to two decimal places.

Rating describes how it compares in professional baseball.

Innings gives the innings and outs recorded.

Per inning shows the earned runs per inning.

WHIP gives walks and hits per inning.

Worth knowing explains unearned runs.

When Should You Use This Calculator?

Tracking a pitcher's season.

Keeping statistics for a youth, school or amateur team.

Checking box score figures.

Comparing pitchers on the same team.

Converting between nine- and seven-inning games.

Common Mistakes

Counting unearned runs.

Using nine innings for a seven-inning game.

Judging a pitcher on a handful of innings.

Comparing ERAs across very different leagues or eras.