parlay_payout: combined odds, payout and implied probability
parlay_payout takes 2 to 20 legs, each with odds and a format, and an optional stake that defaults to 100. It multiplies the decimal odds of the legs into combined odds, then returns the payout and profit if every leg wins and the combined implied probability. It assumes the legs are independent, and one lost leg loses the whole parlay.
Examples are real responses from the live server, captured on 1 November 2026.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
legs | array of { odds, format }, 2 to 20 items | yes | The legs, 2 to 20 items. Each item has odds (a string) and format (american, decimal or fractional). |
stake | number | no | The stake. Defaults to 100. |
What to ask your assistant
Ask: Use BetsBeats to work out a parlay of -110, +150 and 5/2 on a stake of 100.
Example request
Send a tools/call request to the endpoint with the tool name parlay_payout and these arguments.
{
"legs": [
{ "odds": "-110", "format": "american" },
{ "odds": "+150", "format": "american" },
{ "odds": "5/2", "format": "fractional" }
],
"stake": 100
}Real response
A real response for a three-leg parlay. The combined odds come back in American, decimal and fractional form.
{
"legs": 3,
"combined": {
"american": "+1570",
"decimal": 16.7045,
"fractional": "157/10",
"implied_probability": 0.059864,
"implied_probability_percent": 5.986
},
"stake": 100,
"payout": 1670.45,
"profit": 1570.45,
"notice": "For adults 21+ only. Entertainment and analysis; no wins are promised and past results do not predict future ones. BetsBeats does not take bets."
}The math
- Combined decimal odds = the product of each leg's decimal odds.
- Payout = stake x combined. Profit = payout - stake, and it is paid only if every leg wins.
- Combined implied probability = 1 / combined, assuming the legs are independent.
- Worked example: -110 (1.9091), +150 (2.5) and 5/2 (3.5) give 1.9091 x 2.5 x 3.5 = 16.7045. On a stake of 100 the payout is 1670.45 and the profit 1570.45 if all three win. The combined implied probability is 1 / 16.7045 = 0.059864, about 6 percent.
Notes
- Fewer than 2 or more than 20 legs is rejected.
- The profit field is what the parlay would pay if every leg won. It is arithmetic, not a forecast.
- Legs from the same game are often correlated, so the independence assumption can be wrong for them.
Questions
Why is the implied probability so low?
Because every leg has to win. The combined probability is the product of the leg probabilities, so it falls quickly as legs are added.
Can I mix odds formats?
Yes. Each leg has its own format, so American, decimal and fractional legs can sit in one call, as in the example.
Is there a calculator on the site?
Yes, the parlay calculator at /parlay-calculator does the same sum in the browser.
The other tools
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