Parlay calculator: combined odds, payout and the real house edge
Enter each leg as American odds (-110, +200) or decimal odds (1.91). The calculator multiplies the legs, shows the combined price, the payout on your stake and the implied probability — and below it, the table sportsbooks would rather you not see: how their edge compounds with every leg you add.
How the math works
Every parlay is just multiplication. Convert each leg to decimal odds (total return per $1), multiply them, and that product is your parlay's decimal price. Two -110 legs: 1.909 × 1.909 = 3.645 — a $100 stake returns $364.50, roughly +265. The implied probability is 1 ÷ 3.645 = 27.4%. If you want to sanity-check a single leg first, use our odds converter.
The house edge compounds with every leg
A single -110 bet carries about a 4.5% margin across the two sides. In a parlay that margin is baked into each leg, so it compounds. Assuming every leg is a standard -110 coin-flip market, this is what you are actually paying:
| Legs | Parlay pays | Fair odds | House edge |
|---|---|---|---|
| 2 | +264 | +300 | 8.9% |
| 3 | +596 | +700 | 13.0% |
| 4 | +1,228 | +1,500 | 17.0% |
| 5 | +2,436 | +3,100 | 20.8% |
| 6 | +4,741 | +6,300 | 24.4% |
| 7 | +9,142 | +12,700 | 27.8% |
| 8 | +17,544 | +25,500 | 31.1% |
By eight legs the sportsbook keeps close to a third of the fair value — territory we normally associate with lottery tickets. That compounding, not the longshot odds themselves, is why books push same-game parlays so hard.
Correlated legs change the picture
The multiplication above assumes the legs are independent. When they are not — a quarterback's passing-yards over plus his team's moneyline, or a striker to score plus his side to win — the true joint probability is higher than the product, which is why sportsbooks either block those combinations or reprice them inside same-game parlay engines. If a book lets you combine two outcomes that obviously move together at full multiplied price, that is the rare case where the parlay math favors you.
Parlays vs prediction markets
Prediction markets like Kalshi and Polymarket generally do not offer parlays: each contract is a single event priced in cents, and the margin shows up as a spread and fees rather than compounding vig. For a single strong opinion, that pricing model is usually cheaper — we compare the two structures in sportsbook vs prediction market and break down what a trade actually costs in Kalshi vs Polymarket fees.
FAQ
- How are parlay odds calculated?
- Convert each leg to decimal, multiply, apply to your stake. Two -110 legs = 3.65 decimal = about +265.
- How much does a 3-leg parlay pay?
- At -110 per leg: 6.96 decimal, so $100 returns about $696.
- Why are parlays bad value?
- The vig compounds per leg: roughly 8.9% edge at 2 legs, 20.8% at 5, 31.1% at 8.
- What is a correlated parlay?
- Legs that tend to win together. Books block or reprice them because the multiplied price overpays.
