Boost & parlay check

For each leg, every sportsbook's two-sided price is converted to probabilities and the book's cut is removed, so the two sides add to 100%. The middle value across the books is the market's fair probability for that leg. Multiply the legs together and you have the fair chance of the parlay; one divided by that is the fair payout.

Sometimes. Books run some boosts as promotions and price them above fair, usually with a small maximum bet. Many featured parlays are the opposite: several legs, each carrying the book's cut, stacked together. The only way to tell them apart is to price the legs, which is what this does.

Multiplying legs assumes they have nothing to do with each other. Two legs from one game do — a team that covers is more likely to have gone over its team total, for example — so the true chance is not the simple product, and sportsbooks price same-game parlays with their own correlation models. The tool still shows the simple number, but treat it as rough.

No. It is the betting market's own estimate with the fee removed, not our model's number and not a promise. Its use is as a yardstick: a payout well below fair is expensive, a payout above fair is a better deal than the market itself is offering.