THE SPORTS ODDS DESK / EXPLAINED
How to calculate parlay probability
A parlay, also called an accumulator, combines selections into one ticket. For a standard all-win parlay with independent selections, multiply the decimal odds, then divide 100 by that product to get the odds-implied probability as a percentage.
This converts a price into a probability. It does not assess whether a team will win or remove a bookmaker’s margin.
Implied probability (%) = 100 ÷ total odds
A three-leg parlay worked example
Take decimal odds of 1.40, 1.20 and 2.00. Multiplying gives 3.36. Dividing 100 by 3.36 gives 29.7619…, which rounds to 29.8%. The complementary implied probability is 70.2%.
The individual implied probabilities are approximately 71.43%, 83.33% and 50%. Multiplying their unrounded decimal values, 1/1.4 × 1/1.2 × 1/2, gives the same result. Adding or averaging the probabilities would answer a different question.
OPEN THE THREE-LEG EXAMPLE →Two to ten legs at decimal odds of 2.00
Each additional 2.00 selection doubles the combined odds and halves their inverse. This reference assumes every selection has decimal odds of exactly 2.00 and the combined price is their product.
| Legs | Total odds | Implied probability |
|---|---|---|
| 2 | 4.00 | 25.00% |
| 3 | 8.00 | 12.50% |
| 4 | 16.00 | 6.25% |
| 5 | 32.00 | 3.13% |
| 6 | 64.00 | 1.56% |
| 7 | 128.00 | 0.781% |
| 8 | 256.00 | 0.391% |
| 9 | 512.00 | 0.195% |
| 10 | 1024.00 | 0.098% |
When to enter the ticket’s total odds
If the ticket displays a final price after a boost, rounding or a bookmaker adjustment, enter that number in Total odds. For example, final decimal odds of 5.00 imply 20%, regardless of how many games are listed. The calculator pauses the individual fields while a total is entered.
A void or pushed leg can change the settled price under the bookmaker’s rules. This tool does not settle tickets or calculate refunds. Use the revised final decimal price if you want to convert that price.
Why a same-game parlay needs care
Selections from the same game can be related. A team winning and that team scoring many goals are not necessarily independent. Multiplying their individual probabilities does not account for that relationship.
You can convert an offered same-game parlay’s final decimal price using 100 ÷ odds. The result is still a price-implied percentage, not an independently calculated true chance of every event happening.
Why adding a likely selection still changes the ticket
Adding a 1.20 selection to a 5.00 ticket produces 6.00 combined odds in a simple product calculation. The inverse falls from 20% to approximately 16.67%. A short price does not make that extra condition certain.
What this calculator does and does not measure
The tool accepts decimal odds from 1 to 1,000,000,000,000, with up to 30 individual entries. It does not analyze injuries, lineups, prices at other bookmakers or dependencies between games. Bookmaker margins remain in the entered prices. Decimal odds include the stake in their return convention; this calculator focuses on probability, not profit.
For a single-price conversion and a worked margin example, read decimal odds to implied probability.