Calculate combined parlay odds, total payout, and expected value for any number of legs with the PromoGrind Parlay Calculator. Know your math before you place the bet.
Use the calculator →A parlay is a single bet that ties two or more individual wagers together. Every leg must win for the parlay to pay out. In exchange for this added risk, the sportsbook multiplies the odds together, producing a much larger potential payout than any single leg alone. A 4-team parlay at standard -110 odds pays roughly 10-to-1 — tempting on paper, but heavily skewed in the book's favor.
The math is straightforward: convert every leg to decimal odds, then multiply them together. American odds of -110 equals 1.909 decimal; +150 equals 2.50 decimal. A 3-leg parlay of -110/-110/+150 gives 1.909 × 1.909 × 2.50 = 9.12 decimal, meaning a $100 bet returns $912 total. The problem is that each leg already has the vig baked in, so the compounded payout is always less than the true probability would justify.
Sportsbooks earn a higher margin on parlays than on straight bets. A standard -110 two-leg parlay pays 2.6-to-1, but the true odds (removing vig) are closer to 3-to-1. That gap is pure profit for the book. With every additional leg you add, the house edge compounds. This is why recreational bettors tend to lose more on parlays than on singles, and why sharp bettors almost exclusively bet straight.
There are limited situations where parlays have positive expected value. Correlated legs — where winning one leg makes the other more likely — can be mispriced by books that treat them as independent. A classic example: backing the favorite to win combined with the game going under (favorites often control tempo and shorten games). Parlay promos like "parlay insurance" or "SGP boosts" can also flip the math in your favor — run them through the EV calculator before you bet.
Your parlay's break-even probability is simply 1 divided by the decimal payout. A parlay paying 10-to-1 (11.0 decimal) needs to win at least 9.1% of the time to be profitable. If you honestly believe your combined probability is above that threshold, the bet has positive EV. Most bettors overestimate their win rate by 5-10 percentage points — which is exactly why parlays are so costly long-term.