How to Calculate Parlay Payouts and Odds

The sportsbook shows you a parlay payout and you take it on faith. You should not. The math behind a parlay payout takes thirty seconds once you know it, it works for any combination of odds, and running it yourself is how you catch the books quietly paying less than true odds on bundled bets.

The parlay payout formula

Convert every leg to decimal odds, multiply them together, multiply by your stake, and subtract the stake to get profit. That is the whole thing.

Converting American odds to decimal: for minus odds, divide 100 by the number and add 1, so -110 becomes 100/110 + 1, which is 1.909. For plus odds, divide the number by 100 and add 1, so +150 becomes 2.50.

A worked example

Three legs: -110, -150, and +120. In decimal: 1.909, 1.667, and 2.20. Multiply: 1.909 times 1.667 is 3.183, times 2.20 is 7.00. A 50-dollar stake returns 50 times 7.00, which is 350, for 300 in profit. In American terms, that parlay is +600.

Notice the plus-money leg did the heavy lifting. One underdog in a parlay moves the payout far more than another chalky favorite ever will.

Why is the book's payout sometimes lower than the math?

Two reasons. First, some books pay fixed parlay odds on standard -110 legs that are slightly worse than the true multiplication, especially on older-style parlay cards. Three legs at -110 multiply to 6.96, near +596, but a fixed card might pay +580. Second, same-game parlays reprice everything: when legs are correlated, like a quarterback's passing yards and his team's total points, the book adjusts the combined odds well below the simple product, because the legs win together too often.

Either way, the multiplication gives you the honest benchmark to compare against what you are offered.

What does the payout imply about your chances?

Flip the decimal number: 1 divided by the combined decimal odds is the break-even probability. The three-leg example at 7.00 needs to hit more than 1 in 7, about 14.3 percent, to profit long term. Three coin flips hit 12.5 percent. So at true coin-flip legs, that parlay is a money loser, and the gap between 14.3 and 12.5 is exactly the compounded vig you are paying. Your legs need to be better than coin flips by enough to cross that gap before a parlay becomes rational.

Here's the bottom line

Multiply the decimals, and you know the payout. Invert it, and you know the hit rate the parlay demands. Those two numbers turn parlays from lottery tickets into bets you can actually evaluate, and they take less time than refreshing the odds screen. DataStreak's free Bet Calculator does the full calculation instantly for any set of legs, payouts, break-even rate, all of it, so the only question left is whether your legs are good enough.

Calculate any parlay payout instantly with the free DataStreak Bet Calculator.