What is an Unearned Run? Definition, Formula, and Example
An unearned run is a run that scores as the direct result of a fielding error or passed ball rather than the pitcher's own performance, and it counts on the scoreboard but not toward ERA.
What is an Unearned Run?
An unearned run is a run that would not have scored if not for a defensive misplay — a fielding error or a passed ball. It still counts on the scoreboard, and it still counts toward a pitcher's total runs allowed (R), but it's excluded from earned run average (ERA) because the official scorer has ruled the pitcher isn't at fault for it. A single inning can mix earned and unearned runs — some runners score because of the pitcher's own hits/walks allowed, others score only because a defender booted a ball that should have ended the frame.
How It's Calculated
The rule governing this is Official Baseball Rule 9.16. After a fielding error or passed ball occurs, the official scorer mentally reconstructs the inning as if the misplay never happened — assuming the batter is out or the runner is held at the base he would have reached with competent defense. Any run that would still have scored under that hypothetical is earned; any run that only scored because of the removed error is unearned. From there:
ER = R − UER
ERA = 9 × (ER ÷ IP)
Unearned runs are assigned per-run, not per-inning, and they can be reassigned retroactively — MLB's official scoring-changes process sometimes reclassifies a run from earned to unearned (or vice versa) days after the game, once a formal review is completed.
Worked Example
On April 26, 2026, Cubs starter Shota Imanaga worked 5.1 innings (6 H, 3 BB, 6 K) in a 6-0 loss to the Dodgers. During the game, Dodgers catcher Carson Kelly committed a throwing error on a pickoff attempt, which allowed Kyle Tucker to reach base; Tucker later came around to score. MLB's official scorer subsequently reviewed the play and reclassified that run from earned to unearned against Imanaga. The Cubs' final score on the board didn't change and Imanaga's total runs allowed (R) didn't change — but his earned run total, and by extension his ERA, dropped by one run once the reconstruction rule was applied. That's the mechanism in miniature: remove the error, Tucker never reaches, the run he later scores never happens in the reconstructed inning, so it comes off the pitcher's earned line even though it stays on the scoreboard.
Why It Matters
ERA is the sport's most-quoted pitching stat, and the earned/unearned split is what keeps it from unfairly punishing a pitcher for his defense's mistakes. Front offices and analysts use the gap between a pitcher's ERA and his FIP or run-prevention numbers partly to sanity-check whether bad defense (lots of unearned runs) or bad luck on balls in play is dragging down his surface stats. It also matters for team defense evaluation — a staff that consistently allows a high rate of unearned runs points to a fielding problem, not a pitching one, which is exactly the kind of signal DRS and OAA are built to isolate.
Limitations / Common Misconceptions
Unearned runs are not the same thing as "runs that don't matter" — they still lose games and still count in the box score's final tally. The classification also isn't purely mechanical; it involves scorer judgment about what "would have happened" absent the error, which is why calls get revisited and occasionally overturned days later. Don't confuse unearned runs with runs allowed by a reliever who "inherited" baserunners — that's governed by the separate inherited-runner rule, which charges the run to whichever pitcher put the runner on base, independent of earned/unearned status.
Related Terms
In Legends Deck: the simulation engine models fielding independently of pitching, so a card's underlying stuff and command grades aren't dragged down by a defense's errors — unearned runs get generated by the simulated defense, not baked into the pitcher card's rating.