What is RE24? Definition, Formula, and Example
RE24 (Run Expectancy based on the 24 base-out states) measures how many runs a player added or cost his team by tracking the change in expected runs before and after each plate appearance.
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What RE24 Means
RE24 stands for Run Expectancy based on the 24 base-out states. It is a context-aware value stat that credits a hitter, pitcher, or baserunner for the actual change in his team's *expected runs* on every play. The "24" comes from the number of possible game states: 8 baserunner configurations (empty, three single-runner spots, three two-runner spots, and bases loaded) multiplied by 3 out totals (0, 1, 2 outs). A positive RE24 means the player produced more runs than an average outcome would have; a negative RE24 means he cost his team expected runs.
How RE24 Is Calculated
Analysts first build a run expectancy matrix from years of play-by-play data — the average number of runs a team scores from the end of each base-out state to the end of the inning. Standard values look like this:
- Bases empty, 0 outs: ~0.48 runs
- Runner on first, 0 outs: ~0.85 runs
- Runner on second, 0 outs: ~1.10 runs
- Bases loaded, 0 outs: ~2.29 runs
- Bases empty, 2 outs: ~0.10 runs
For each plate appearance, RE24 is:
RE24 = (RE after the play − RE before the play) + Runs scored on the play
Sum that figure across every plate appearance and you get a player's season RE24. Because it uses *actual* base-out states, RE24 rewards production in higher-run situations more than a context-neutral stat like wRC+ does.
Worked Example
Imagine a hitter steps up with a runner on second and nobody out (RE = 1.10) and doubles him home. Run expectancy after the play is a runner on second, 0 outs again (1.10), plus 1 run scored. His RE24 for that play is (1.10 − 1.10) + 1 = +1.00 run. Now suppose another hitter comes up bases loaded, 0 outs (RE = 2.29) and strikes out, leaving the bases loaded with 1 out (RE = 1.54). His RE24 is (1.54 − 2.29) + 0 = −0.75 runs — a real cost, because he squandered a huge scoring chance. Over a full season, an elite middle-of-the-order bat commonly finishes around +40 to +50 RE24, while a replacement-level hitter lands near zero or negative.
Why RE24 Matters
RE24 bridges the gap between rate stats and real, on-field run impact. Front offices use it to see who actually moved the run-expectancy needle, and it underpins linear-weights stats like wOBA and the run values behind Stuff+. For pitchers, RE24 captures the value of stranding inherited runners — a strength that ERA hides.
Limitations and Common Misconceptions
RE24 is context-dependent, so it is not a pure measure of talent — a hitter with more bases-loaded chances has more RE24 to gain than one who bats with the bases empty all year. That makes it great for *describing what happened* but weaker for *predicting future performance*; for forecasting, prefer context-neutral metrics. RE24 also ignores score and inning — it treats a 1st-inning double and a 9th-inning double identically, which is where WPA and Leverage Index take over. Don't confuse RE24 with WPA: RE24 counts runs, WPA counts win probability.
Related Terms
In Legends Deck: the same run-expectancy matrix that powers RE24 drives our in-game scoring engine. Every simulated plate appearance updates the base-out state and its expected runs, so the outcomes your legends produce are weighted by exactly how much they shift a team toward scoring — the same logic real analysts use to value a season.