How it works
A parlay is one bet on several legs, and it wins only if every leg wins. Its price is every leg’s decimal price multiplied together, so each leg multiplies the payout. The implied chance is 1 ÷ that price.
Give your own chance for each leg and the calculator multiplies those too, for the parlay’s combined chance and its expected value. That step assumes the legs are independent: that one leg winning says nothing about another.
The formula
Parlay decimal = d1 × d2 × … × dn
Implied chance = 1 ÷ parlay decimal
Payout = stake × parlay decimal
Your combined chance = p1 × p2 × … × pnOnly for independent legs.
EV per $1 = combined chance × parlay decimal − 1
A worked NFL example
Three NFL legs at −110 each, say two spreads and a total from three different games, for $10.
- Each leg in decimal
- 1.9091
- Parlay price: 1.9091 × 1.9091 × 1.9091
- 6.958
- In American odds
- +596
- Implied chance: 1 ÷ 6.958
- 14.37%
- Payout on $10, if all three win
- $69.58
If each leg is a true coin flip, the parlay’s real chance is 50% × 50% × 50% = 12.5%, and its EV is −13.0%. One leg alone at −110 has an EV of −4.5%: the margin compounds with every leg.
| Price | Implied | EV | |
|---|---|---|---|
| 1 leg (a single bet) | −110 | 52.38% | −4.5% |
| 2 legs | +264 | 27.44% | −8.9% |
| 3 legs | +596 | 14.37% | −13.0% |
| 4 legs | +1228 | 7.53% | −17.0% |
| 6 legs | +4741 | 2.07% | −24.4% |
Common mistakes
- Expecting more legs to add value. Each leg multiplies its margin in along with its payout. Unless your chance beats the price on the legs, more legs lose more on average, as the table shows.
- Multiplying same-game legs. A team’s spread and the game total, or a quarterback’s passing yards and the team’s points, tend to move together. For legs like these the real chance can be well above or below the product, so treat the combined chance as a rough guide.
- Forgetting pushes and voids. A leg that pushes or is voided changes the payout, under rules each book sets. This calculator prices every leg as a win.
- Comparing payouts, not chances. A bigger payout is the price of a longer shot, not a better deal. Compare the implied chance with your combined chance.
In Unitley
Unitley’s Parlay Builder builds parlays of 2 to 25 legs from main lines and NFL player props, with the combined odds, your chance per leg, the EV and a same-game warning. See the Parlay Builder.