How do you check a parlay's EV?

A parlay's expected value is worked out by finding the true chance that every leg wins, then comparing that chance to the payout the sportsbook quotes. The true chance does not come from the price on the slip, and it does not come from a second sportsbook. It comes from simulating the games those legs live in, thousands of times each, and counting how often the whole ticket would have landed.

Written by Jesse, NegativeEV. Last updated 12 August 2026.

Is a parlay worth it?

That is a question about the price of the specific legs. Are parlays worth it? answers it.

This page covers the mechanics instead: where the true probability comes from, how correlated legs are handled, and what a check returns.

How do you work out a parlay's expected value?

Grade each leg against simulated games to get its true probability, combine the legs into one true probability for the whole ticket, then set that probability against the quoted payout. The gap between them is the ticket's expected value.

A leg's true probability is not the one its price implies. Each leg is graded against thousands of simulated runs of its own game rather than against another book's number. Legs in different games are independent, and only there do the probabilities multiply.

Why do correlated legs change the price?

Because legs in the same game move together, so multiplying them as if they were independent gets the ticket's real chance wrong.

Legs	How they are combined	Why
In different games	Their probabilities multiply	The games do not affect each other
In the same game	Counted together across the same simulated games	The legs rise and fall together, so multiplying them misstates the ticket's real chance

Two props on the same batter, or a total and a moneyline in one game, rise and fall together. Books reprice same-game parlays with that correlation in mind. Legs from the same game are therefore counted together across the same simulated games, so their correlation is kept instead of assumed away.

What does a parlay check return?

A true win probability for the whole ticket and the expected value at the quoted odds.

Paste the parlay or upload a screenshot of the slip. Every leg is read out, matched to its game and priced. If a leg cannot be graded, the ones that remain are re-priced on their own rather than guessed at. MLB, WNBA, PGA, and ATP bets are covered. Ten free checks a day, unlimited when signed in.

What can a parlay EV check not do?

Price a leg that is not on a simulated slate.

A bet on a game the simulator has not run comes back ungraded rather than guessed at, and a ticket with an ungraded leg is priced on the legs that remain. The number is also a probability, not a prediction. A ticket that grades as unlikely still lands sometimes, and a ticket that grades as likely still misses.

Background: how sim-grading works.

Work out the payout first: parlay calculator.