How the score is calculated
V is the change in expected runs for the challenging team if ABS corrects the call, from 2026 count, out and base run values. C is the expected run value of the challenges a team gives up when a challenge fails, averaged over 2026 games in the same inning, half, outs, home or away and score situation. CT = C / (V + C) is the success rate at which the challenge breaks even in modeled runs, and DOS = 100 × (1 − CT). A higher DOS means a bigger opportunity relative to what is at risk.
Values come from the frozen CT-S1 standard, using its September 11–27, 2026 confirmation schedules. When a situation is too rare for an exact estimate, the cost comes from a broader group of situations, and the calculator says so. Extra innings have no CT-S1 value, and in the 8th and 9th innings the calculator shows no score when there were too few 2026 games with the entered score to estimate the cost. Under the CT-S1 reference, a team is assumed to challenge any call worth at least about 0.08 runs, so through about the 7th inning there is more than enough game left to use both challenges and the cost of losing one stays roughly flat; it falls only late in the game. These are 2026 regular-season values; postseason games use them as a reference, not as a separate estimate. The full method, data window and limitations are in the CT-S1 methodology.
DOS describes the situation. It does not say whether a player should have challenged, how likely the call was to be wrong, or how good any player's judgment is. CT-S1 values expected runs, not win probability.
