Free Parlay Calculator | MLB Parlay Odds & Payout | Mongoose Bets
Parlay Calculator
Combined odds, payout, and correlation warnings for up to 12 legs.
Enter odds for at least 2 legs to see the combined parlay.
How parlay odds are calculated
A parlay multiplies each leg's decimal odds together. If you combine three legs at -110, -120, and +150:
- -110 → 1.909 decimal
- -120 → 1.833 decimal
- +150 → 2.500 decimal
- Combined: 1.909 × 1.833 × 2.500 = 8.75 decimal (≈ +775 American)
At +775, a $10 stake returns $87.50 (profit of $77.50). Sounds great. But the implied probability of all three legs hitting is about 11.4% — and each leg independently only needed to hit 52.4%, 54.5%, and 40% respectively for the parlay to break even. Parlay math punishes correlated legs and rewards sportsbooks with tall vig stacks.
Why correlated parlays are different
If you stack "Yankees win" with "Yankees game total over", those outcomes are positively correlated— when the Yankees score a lot, they also tend to win. The naive combined odds assume the two events are independent, so they understate the true joint probability. If the book pays you naive parlay odds on a correlated parlay, the parlay is often positive expected value. This is why most books restrict or deny certain same-game correlated stacks.
Other stacks are negatively correlated — for example, pitcher strikeouts over combined with opposing team total over. When the pitcher strikes more batters out, the opposing team scores fewer runs. Naive parlay odds overstate the joint probability here, so the parlay is -EV.
For live sim-derived joint-probability parlays on today's slate, see Prop Finder — it computes correlated edges against book-implied fair odds using the actual 2,500-sim output.
Round-robin parlays
A round-robin is every N-leg combination of your selections. Pick 4 legs and "round-robin by 3" — you get 4 separate 3-leg parlays (one for each possible combination of 3-of-4 legs). Each is wagered independently. The appeal: losing one leg only loses one of the round-robin parlays, not all of them. The catch: you're placing 4 bets instead of 1, so your total stake is 4× higher.
This calculator focuses on single parlays. For round-robins, the math is the same per-combination — just run the calculator once per combination.
Bankroll reality check
Most long-run losing sports bettors lose on parlays, not straight bets. Parlays turn a modest per-leg edge into a compounded vig drag. A 4-leg parlay at -110/leg bleeds roughly 4 × 4.76% = 19% in accumulated vig. Unless each leg carries meaningful positive expected value and is uncorrelated with the others, parlays underperform straight bets on identical legs.
Frequently asked questions
- How are parlay odds calculated?
- Multiply each leg's decimal odds together, then convert the combined decimal back to American. A -110 leg is 1.909 decimal; three -110 legs combine to 1.909^3 ≈ 6.96 decimal, or about +596 American.
- What's the maximum number of legs in a parlay?
- Sportsbooks typically allow 10-25 legs depending on the market and the book. This calculator supports up to 12 legs. The math scales identically for any number.
- Are correlated parlays profitable?
- They can be. When legs are positively correlated (e.g., Yankees ML + Yankees team total over), the true joint probability is higher than the naive product of independent probabilities — so if the book pays naive parlay odds, the parlay is +EV. Most books limit or reject known-correlated parlays precisely because of this.
- What's a round-robin parlay?
- A round-robin places every N-leg combination of your selections as a separate parlay. Pick 4 legs and round-robin by 3 and you get four 3-leg parlays. Losing one leg loses only one of the four parlays, but you've placed 4× the stake total.
For today's actual +EV MLB bets run through 2,500 Monte Carlo simulations, see Best Bets →