Power In The Prize
Recreate a -1 run line by splitting your stake between the moneyline and the -1.5 run line, sized so a 1-run win breaks exactly even.
The whole difference between these two lines comes down to what happens when the favorite wins by exactly one run — which, in baseball, happens a lot.
Roughly a quarter to a little over a quarter of MLB games are decided by a single run. If your favorite wins 4-3, a -1.5 bet loses outright — the run line wasn't covered. A -1 bet on the same game just pushes: you get your stake back, no harm done.
That protection isn't free — sportsbooks price -1 with worse odds (more negative, or less positive) than -1.5, since they're giving up the chance to collect on every one-run win. But the calculator above shows you exactly what that trade costs in dollar terms for the specific odds you're looking at, so you can judge whether the insurance is worth the price on any given game.
Generally, -1 tends to be the sharper side when the price gap between the two lines is small, and when you're betting a team that plays a lot of close, low-scoring games. If the -1 line is priced dramatically worse, the standard -1.5 might still be the better expected-value play — that's exactly what the breakdown above is for.