Free tool
Add your legs, set a stake, and see the combined odds, payout, and profit instantly. Pure math, no signup.
Each leg's American odds convert to a decimal multiplier; the multipliers multiply together, and the result converts back to American odds and a payout on your stake. This calculator does the conversion for any number of legs.
The book's margin on every leg compounds. Two legs at -110 each carry roughly double the hold of a single bet, and it grows with each added leg — the payout looks big because the true probability is small.
Payout is what the book returns including your stake; profit is the payout minus the stake. The calculator shows both so there's no ambiguity at the window.
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The honest explainer
A parlay multiplies decimal prices — and, because each price includes margin, it multiplies the book's cut too. The payout grows geometrically while your chance of collecting shrinks geometrically. Both facts are the same multiplication.
This calculator shows the honest combined price of independent legs. That word — independent — is load-bearing: legs from the same game don't multiply cleanly, which is why books route those through SGP pricing instead.
Three legs at −110 each: decimal 1.909³ = 6.96, listed as roughly +596. If each leg is a true coin flip, the parlay hits 12.5% of the time — fair decimal 8.00. You're being paid 6.96 for an 8.00 shot: about 13% total margin, versus ~4.5% on a single −110 bet. Each added leg compounds the cut.