ERA Calculator

1. Enter earned runs (ER) — runs scored against the pitcher that weren't caused by fielding errors. Unearned runs don't count toward ERA.
2. Enter innings pitched (IP) in baseball notation: .1 means 1 out, .2 means 2 outs. So 45.2 IP = 45 and 2/3 innings = 45.667. The calculator handles the conversion automatically.
3. The calculator multiplies ER by 9, divides by IP, giving the ERA — the average earned runs allowed per 9 innings.
4. Compare to the tier table: under 3.00 is elite, 3.00-4.00 is solid, 4.00-4.50 is league average. Above 5.00 over a full season usually means a roster move.

ERA (Earned Run Average) is one of baseball's oldest stats, normalized to a 9-inning game so pitchers with different workloads can be compared directly.

ERA = (Earned Runs × 9) / Innings Pitched

Where:
Earned Runs = runs scored against the pitcher without fielding errors
Innings Pitched = full innings + (outs / 3)

Example: A starter gives up 12 earned runs over 45⅔ innings (written 45.2 in box scores).

• IP in decimal form = 45 + 2/3 = 45.667
• ERA = (12 × 9) / 45.667 = 2.36 ERA

That's elite — the pitcher is allowing 2.36 earned runs per 9 innings, well below the typical MLB starter average of ~4.20.

ERA has been baseball's standard pitching stat since 1912, but it has well-known flaws. A pitcher's ERA depends not just on how they pitch, but on the defense behind them, the ballpark dimensions, and luck. Modern stat analysis uses three additional measures:

Three observations from modern pitching data:

• Single-season ERA is noisy. A pitcher's ERA can vary ±0.50 year to year purely from defensive variance and ballpark factors. FIP is more stable.
• Park-adjusted ERA (ERA+) matters for comparison. A 3.50 ERA at Coors Field is far better than a 3.50 ERA at Petco Park, because Coors Field inflates offense significantly. ERA+ over 100 means above league average.
• Career ERA below 3.00 is Hall of Fame territory in the modern era. Pedro Martinez (2.93), Greg Maddux (3.16), Roy Halladay (3.38), and Clayton Kershaw (~2.50) are reference points. Only a handful of starters maintain sub-3.00 over 10+ seasons.