Distinguish the payout from the chance of winning
Multiplying leg prices estimates the payout of a standard parlay. Two −110 legs each have decimal odds of 1.90909, giving combined odds of 3.64463. A $25 stake returns about $91.12 if every leg wins; $66.12 of that is net profit. The inverse price, about 27.44%, is a break-even probability implied by that combined price.
Independence matters for probabilities
The actual probability of winning every leg is not automatically the inverse of the price. If two events each have a 55% chance and are independent, their joint probability is 30.25%. If they are correlated, multiplying 55% by 55% is not valid. Events involving the same player or game often share information and should not be assumed independent.
Use the sportsbook’s actual offer
Same-game parlays may be repriced for correlation, and boosts can change the final offer. This calculator multiplies the individual prices you supply; it does not reproduce a bookmaker’s same-game pricing engine. When an actual combined price is available, use that price and your estimated joint probability in the EV calculator.
Check voids, pushes and settlement
A voided leg may reduce the payout, while other rules can settle a ticket differently. A losing leg commonly loses the ticket, but the applicable bookmaker rules control the outcome. Adding more legs increases the number of conditions that must be met and compounds pricing margins; a larger displayed payout does not by itself mean better value.
Examples are hypothetical and rounded. These calculators explain arithmetic; they do not establish a model’s accuracy or guarantee an outcome.