🎯 Parlay Calculator
Enter your stake and add the odds for each leg of your parlay. The calculator will show combined odds, potential payout, true probability, and effective house edge.
Payout Breakdown
📖 How Parlay Odds Work
Parlay Calculation: Multiply the decimal odds of each leg together. For example, three legs at 1.90 × 1.85 × 2.10 = 7.38 combined decimal odds. Your potential payout = Stake × Combined Odds.
Parlays (also called accumulators, multis, or combo bets) combine multiple individual wagers into a single bet. All selections must win for the parlay to pay out. While the potential returns are higher, the probability of winning decreases with each added leg.
| Number of Legs | Example (at -110 each) | Win Probability* | Approx. House Edge |
|---|---|---|---|
| 2 Legs | 2.64x payout | 25% | ~9.5% |
| 3 Legs | 4.81x payout | 12.5% | ~13.8% |
| 4 Legs | 8.76x payout | 6.25% | ~18.5% |
| 5 Legs | 15.96x payout | 3.1% | ~22.6% |
| 6 Legs | 29.08x payout | 1.6% | ~26.5% |
*Assumes 50/50 fair odds; actual probability depends on the events.
Why Sportsbooks Love Parlays: The house edge compounds with each leg. A single -110 bet has ~4.5% edge. But a 5-leg parlay at -110 per leg has ~22.6% effective edge—that's why sportsbooks heavily promote parlay betting with bonuses and "odds boosts."
Understanding Parlay Betting: Mathematics and Strategy
A parlay (known as an accumulator in the UK, or multi-bet in Australia) is a single wager that links together two or more individual bets. According to the American Gaming Association's sports betting glossary, all selections in a parlay must win for the bet to pay out. If any selection loses, the entire parlay loses.
The appeal of parlays is the multiplied payout—combining three 2.00 odds bets creates an 8.00 odds parlay, turning a $10 wager into a potential $80 return. However, this comes at a significant cost: the probability of winning decreases exponentially with each added leg.
The Mathematics Behind Combined Odds
Parlay odds are calculated by multiplying the decimal odds of each individual selection. According to probability theory as documented by Britannica, when events are independent, you multiply their probabilities together:
- Two 50% chances: 0.50 × 0.50 = 0.25 (25% combined probability)
- Three 50% chances: 0.50 × 0.50 × 0.50 = 0.125 (12.5% combined probability)
- Four 50% chances: 0.50 × 0.50 × 0.50 × 0.50 = 0.0625 (6.25% combined probability)
This exponential decay is why parlays are mathematically unfavorable for bettors. While a single -110 bet has a house edge of approximately 4.5%, the edge compounds multiplicatively in parlays. Research from sports betting analytics firms consistently shows that parlay bets have some of the highest profit margins for sportsbooks—often 15-30% compared to 4-5% for straight bets.
Why the House Edge Compounds in Parlays
The compounding house edge is the hidden cost of parlay betting. Here's how it works mathematically:
For a fair coin flip (50% probability), fair decimal odds would be 2.00. But sportsbooks offer -110 American odds (1.909 decimal) on each side of a typical point spread. This builds in their 4.5% margin. When you multiply these slightly reduced odds together across multiple legs, the disadvantage multiplies:
- Single bet: 1.909 vs fair 2.00 = 4.5% edge
- 2-leg parlay: 3.646 vs fair 4.00 = 8.9% edge
- 3-leg parlay: 6.963 vs fair 8.00 = 13.0% edge
- 4-leg parlay: 13.30 vs fair 16.00 = 16.9% edge
This mathematical reality is why professional bettors rarely make parlay bets. As explained in our guide to betting systems, the house edge cannot be overcome through clever bet structuring—it's built into the mathematics.
Same-Game Parlays: An Even Worse Deal
Same-game parlays (SGPs) combine multiple bets from a single event—like a player to score, team to cover the spread, and game to go over the total. While popular with casual bettors, SGPs typically offer even worse value than traditional parlays.
The reason is correlation. In a traditional parlay, events are independent (the Lakers game doesn't affect the Yankees game). But in SGPs, outcomes are correlated—if a team's star scores 30+ points, the team is more likely to cover the spread. Sportsbooks adjust the odds to account for this correlation, usually reducing the parlay multiplier. According to industry analysis from the Legal Sports Report, SGP margins often exceed 20-25%.
When Parlays Might Make Mathematical Sense
Despite their poor expected value, there are limited scenarios where parlays can be strategically justified:
- Correlated underdogs: If you believe two outcomes are positively correlated but priced independently, a parlay captures that correlation
- Positive expected value legs: If each leg has positive EV (your true probability exceeds implied probability), the parlay preserves that edge—see our Kelly Criterion Calculator
- Entertainment value: Small parlays for entertainment, with money you've budgeted for losses, are fine if you understand the mathematics
- Promotional offers: "Parlay insurance" or "odds boosts" can occasionally shift the math in your favor
Calculating Your Own Parlay Edge
To determine if a parlay has value, you need to estimate the true probability of each leg winning. If your estimated combined probability exceeds the implied probability from the offered odds, the parlay has positive expected value. This is where tools like our Probability Calculator become essential.
For deeper analysis of variance and expected value in multi-bet scenarios, review our comprehensive guide on variance and expected value in gambling.
Frequently Asked Questions
What is a parlay bet?
A parlay (also called accumulator, combo, or multi-bet) combines multiple individual bets into one wager. All selections must win for the parlay to pay out. The odds are multiplied together, creating higher potential payouts but much lower probability of winning. Parlays are popular because of the large potential returns, but they have a higher house edge than straight bets.
How are parlay odds calculated?
Parlay odds are calculated by multiplying the decimal odds of each leg together. For example, three bets at 2.00 odds each = 2.00 × 2.00 × 2.00 = 8.00 combined decimal odds. Your potential payout is your stake multiplied by the combined odds. In American odds, you'd convert each leg to decimal first, multiply, then convert back if needed.
Why do parlays have a higher house edge?
The house edge compounds with each leg because you're multiplying the slightly reduced odds (from the sportsbook's margin) across all selections. If each bet has a 5% house edge, a 4-leg parlay doesn't have 5% edge—it has approximately 18.5% effective edge. This compounding effect is why sportsbooks heavily promote parlays with bonuses and special offers.
What is a same-game parlay (SGP)?
A same-game parlay combines multiple bets from a single event—like player props, spreads, and totals from one game. SGPs often have correlated outcomes (if a player scores many points, their team is more likely to win), so sportsbooks adjust the odds accordingly. This adjustment typically results in even worse value than traditional parlays, with house edges often exceeding 20-25%.
What happens if one leg of my parlay pushes?
When a parlay leg pushes (ties), that selection is typically removed from the parlay, and the odds are recalculated with the remaining legs. For example, a 4-leg parlay with one push becomes a 3-leg parlay. Some sportsbooks have different push rules, so always check the terms. If all remaining legs win, you still get paid—just at lower odds than the original parlay.
Are parlays ever a good bet?
From a pure expected value perspective, parlays are almost never optimal because of the compounding house edge. However, they can be justified for entertainment (with money budgeted for losses), when exploiting promotional offers like parlay insurance, or when all legs have positive expected value based on your own probability estimates. Professional bettors typically avoid parlays and stick to straight bets.
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