A parlay calculator takes the odds of two or more individual bets, multiplies them in decimal form, and returns the combined payout if every leg wins. The math is straightforward, but the strategic question — whether the parlay is actually a positive-expected-value (+EV) bet — is where most bettors lose money. This page walks through the formula, gives you a reference payout table, and explains when a parlay is worth placing.
How a Parlay Calculator Works
A parlay combines multiple bets into a single wager. All legs must win for the parlay to cash. The payout is calculated by multiplying the decimal odds of every leg together, then multiplying by the stake. If any leg loses, the entire parlay loses — there is no partial credit (except in same-game parlay pushes, which return that leg’s stake).
The reason parlays look attractive is the compounding payout. The reason they are mathematically punishing is that the implied probability also compounds. A 2-leg parlay at -110/-110 has roughly 23.9% implied probability, but the true win probability for two coin-flip legs is closer to 25% — sportsbooks bake their margin into every leg, and that margin compounds with every additional leg.
The Math: Multiplying Decimal Odds
The core formula is simple:
Parlay Decimal Odds = Leg 1 Decimal × Leg 2 Decimal × … × Leg N Decimal
Parlay Payout = Stake × Parlay Decimal Odds
Decimal odds include the return of the stake. A leg at decimal 1.91 (equivalent to American -110) means a $100 bet returns $191 total — $91 profit plus the $100 stake. To convert American odds to decimal, use these formulas:
- Negative American odds: Decimal = (100 / |American|) + 1
- Positive American odds: Decimal = (American / 100) + 1
Example: A 3-leg parlay with legs at -110, -150, and +120 converts to decimals of 1.909, 1.667, and 2.200. Multiplied together, parlay decimal odds = 7.001. A $100 stake returns $700.10, for a profit of $600.10.
Parlay Payout Examples (2-Leg, 3-Leg, 5-Leg, 10-Leg)
The table below shows payouts on a $100 stake when every leg is priced at the industry-standard -110 (decimal 1.909). Real-world parlays mix odds, but -110 is the cleanest baseline for understanding how the curve steepens with each added leg.
| Legs | Parlay Decimal Odds | American Odds (approx) | $100 Bet Returns | Profit |
|---|---|---|---|---|
| 2 | 3.645 | +264 | $364.50 | $264.50 |
| 3 | 6.957 | +595 | $695.70 | $595.70 |
| 4 | 13.281 | +1,228 | $1,328.10 | $1,228.10 |
| 5 | 25.348 | +2,434 | $2,534.80 | $2,434.80 |
| 10 | 642.575 | +64,157 | $64,257.50 | $64,157.50 |
A 10-leg parlay at -110 per leg pays roughly 642-to-1, but the implied probability is only about 0.156%. To break even long-term, your true win rate on each leg would need to clear 52.4% — and across ten correlated decisions, that is exceptionally hard.
American Odds to Decimal Odds Conversion
Most U.S. sportsbooks display American odds by default. Use the reference below to convert quickly, then multiply the decimals together for any parlay.
| American Odds | Decimal Odds | Implied Probability |
|---|---|---|
| -200 | 1.500 | 66.67% |
| -150 | 1.667 | 60.00% |
| -110 | 1.909 | 52.38% |
| -105 | 1.952 | 51.22% |
| +100 | 2.000 | 50.00% |
| +110 | 2.100 | 47.62% |
| +150 | 2.500 | 40.00% |
| +200 | 3.000 | 33.33% |
Same Game Parlays — Why the Math Changes
A traditional parlay calculator assumes every leg is independent. In a same game parlay (SGP), legs are correlated — a quarterback throwing for 300+ yards is positively correlated with his top receiver going over receiving yards. Sportsbooks know this and re-price SGP payouts downward to account for correlation.
That re-pricing is usually conservative, which means there are SGP combinations where the book has under-corrected and the true combined probability is higher than the offered price implies. PropsBot’s SGP module flags these correlated combinations across NBA, NFL, MLB, NHL, and PGA — the same model that produces our best NBA bets today output also surfaces parlay legs whose joint probability beats the posted parlay odds.
When a Parlay Has +EV (And When It Doesn’t)
A parlay is +EV when the product of your true probabilities for each leg exceeds the implied probability of the parlay price. The trap is that most bettors estimate each leg’s edge optimistically. If your true edge on each leg is 2%, a 5-leg parlay compounds that edge — but it also compounds any modeling error.
Across 218,000+ audited graded picks, the parlay legs that consistently produce +EV share two traits: (1) each individual leg already clears a +EV threshold as a standalone bet, and (2) the correlation between legs is either neutral or positive. Stacking lottery-ticket longshots together does not create edge — it compounds variance.
How PropsBot Flags +EV Parlay Combinations
PropsBot’s model produces a probability distribution for every player prop and game line across NBA, NFL, MLB, NHL, and PGA. Our performance methodology documents how those probabilities are calibrated against closing-line value — for MLB specifically, our Brier score of 0.1903 outperforms Vegas closing lines at 0.1947, and our audited NBA ROI sits at +25.1% with MLB at +31.7%.
For parlays, the SGP builder takes the model’s joint probability output and compares it against the sportsbook’s offered SGP price. When joint model probability beats implied probability, the leg combination is flagged. The same logic applies to cross-game parlays, where independence is a safer assumption.
You can see the flagged combinations on the free tier alongside our public daily picks, or get the full slate at $34.99/mo. If you’re comparing tools, our best AI player prop tools 2026 breakdown and our Rithmm review cover where PropsBot’s parlay-flagging differs from competitors.
FAQ
How is a parlay payout calculated?
Convert every leg’s American odds to decimal, multiply the decimals together to get parlay decimal odds, then multiply by your stake. The result is the total return (stake plus profit).
What does a 4-team parlay pay at -110 per leg?
Roughly +1,228 American odds, or about $1,228 profit on a $100 stake. The exact decimal is 1.909^4 = 13.281.
Are parlays ever a smart bet?
Only when each leg independently clears a +EV threshold and the correlation between legs is favorable. Lottery-ticket parlays — stringing together longshots for the big payout — are negative-EV in almost every case.
What happens if one leg pushes?
Most sportsbooks reduce the parlay by that leg. A 4-leg parlay with one push becomes a 3-leg parlay, and the payout is recalculated using only the winning legs.
Do same game parlays use the same math?
No. SGPs adjust for correlation between legs in the same game, so the payout is lower than a naive multiplication would suggest. The model has to account for joint probability, which is why PropsBot’s SGP module computes joint distributions rather than independent products.
What’s the breakeven win rate for a parlay?
Per leg at -110, breakeven is 52.38%. Across a parlay, breakeven on the parlay itself is 1 divided by parlay decimal odds. A 3-leg parlay at +595 needs to win roughly 14.4% of the time to break even.
Where can I see PropsBot’s flagged parlay combinations?
The free tier exposes daily public picks including flagged SGP legs. The full slate across NBA, NFL, MLB, NHL, and PGA is available at the paid tier. Reference pages include free NBA picks, free MLB picks, free NFL picks, and the full glossary.
