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.
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.