Run Line vs Moneyline in Baseball
A moneyline asks whether the selected team wins. A -1.5 run line asks whether it wins by at least two runs; +1.5 also covers a one-run loss. Comparing these markets requires probabilities for different events and each event’s offered payout.
Define the margin from the selected team’s perspective
Let M be the selected team’s final runs minus its opponent’s runs under the quoted settlement rules. Moneyline success is M > 0; -1.5 success is M ≥ 2; +1.5 success is M ≥ −1. A one-run win loses at -1.5; it is not a push.
A league-wide frequency of games decided by one run does not tell you how often a particular favorite wins by multiple runs. The denominator matters: P(win by 2+) equals P(win) × P(win by 2+ given a win). Use the selected team, not whichever team happened to win the historical game.
Compare both expected returns
Hypothetical inputs: P(win) = 70% and P(win by 2+ given a win) = 80%. Then P(win by 2+) = 0.70 × 0.80 = 56%. At moneyline -200, the decimal return is 1.50 and break-even is 66.6667%; expected net return per unit is 0.70 × 1.50 − 1 = +5.00%. At run line -1.5 priced -120, decimal return is 1.8333333 and break-even is 54.5455%; expected return is 0.56 × 1.8333333 − 1 = +2.6667%.
Both modeled expectations are positive, yet the moneyline has the higher expected return per unit under these assumptions. Clearing the run-line threshold does not make it the better choice. The comparison excludes fees, pushes, and voids and assumes the quoted prices are available. Estimated probabilities can be wrong.
If the conditional multi-run share were instead 70%, the unconditional cover probability would be 49% and the run-line expected return would be −10.1667%. This sensitivity illustrates why a heavy-favorite label cannot substitute for a margin forecast.
Build and test a margin forecast
Consider expected starter workload, available relievers, confirmed lineups, venue, and the full distribution of runs. Do not designate the bullpen as the largest factor without measuring that claim. A forecast of average runs alone does not determine the chance of a multi-run win.
To investigate historical cover rates, retain the competition, seasons, regular-season or postseason scope, game IDs, final scores, selected-side prices, and quote times. Separate conditional win margins from unconditional covers. Evaluate returns at the prices actually recorded; an aggregate cover frequency is not proof that a current quote has value.
Continue reading: Starting Pitcher Value · Implied Probability.
Frequently Asked Questions
Does winning by one run push a -1.5 selection?
No. A one-run win loses at -1.5. The selected team must win by two or more runs.
Does clearing the run-line break-even rate make it better than the moneyline?
No. Calculate expected net return at both offered prices using the appropriate probabilities and uncertainty. In the hypothetical example, the moneyline expectation is +5.00% and the run-line expectation is +2.6667%.
Can I multiply two unconditional win rates?
No. For the calculation here, multiply the chance of winning by the chance of a multi-run win conditional on winning. A league-wide margin frequency is a different quantity.