How are parlay odds calculated?

Convert every leg to decimal odds, multiply them together, then convert the product back. Three legs at -110 are 1.909 each, and 1.909 x 1.909 x 1.909 is 6.96 — about +596 in American odds. American odds cannot be multiplied directly, which is the most common way a hand calculation goes wrong.

Does adding a leg increase the payout?

Yes, and it reduces the chance of winning by at least as much. Each leg multiplies the price and multiplies the probability of the whole bet failing. A parlay pays more because it wins less often, not because it is better value.

Can this calculator price a same game parlay?

No, and neither can any calculator that only knows the prices. Selections from the same game are correlated — a quarterback throwing for 300 yards and his team winning are not independent events — so multiplying their odds overstates the true price. Sportsbooks use their own correlated models for these.

What does the implied chance figure mean?

It is one divided by the combined decimal odds: what the price says about how often the parlay should win, before any sportsbook margin is removed. Because every leg carries its own margin, the real probability is lower still.

Free calculator

Parlay Calculator

Work out what a parlay pays. Enter each leg in American odds, add a stake, and see the combined price, the implied chance and the total return.

Your legs

American odds, e.g. -110 or +150

Leg 1
Leg 1 odds
1.90952.4%
Leg 2
Leg 2 odds
1.90952.4%
Leg 3
Leg 3 odds
2.50040.0%

3 of 12 legs

Payout

Stake

Combined odds (3 legs): +811
Decimal: 9.112
Implied chance: 10.98%
Stake: $100.00
Profit if it wins: $811.16
Total payout: $911.16

Every leg must win. The combined price is the product of the decimal odds, which is why adding a leg multiplies the payout and divides the chance.

Frequently asked questions

How are parlay odds calculated?: Convert every leg to decimal odds, multiply them together, then convert the product back. Three legs at -110 are 1.909 each, and 1.909 x 1.909 x 1.909 is 6.96 — about +596 in American odds. American odds cannot be multiplied directly, which is the most common way a hand calculation goes wrong.
Does adding a leg increase the payout?: Yes, and it reduces the chance of winning by at least as much. Each leg multiplies the price and multiplies the probability of the whole bet failing. A parlay pays more because it wins less often, not because it is better value.
Can this calculator price a same game parlay?: No, and neither can any calculator that only knows the prices. Selections from the same game are correlated — a quarterback throwing for 300 yards and his team winning are not independent events — so multiplying their odds overstates the true price. Sportsbooks use their own correlated models for these.
What does the implied chance figure mean?: It is one divided by the combined decimal odds: what the price says about how often the parlay should win, before any sportsbook margin is removed. Because every leg carries its own margin, the real probability is lower still.

How parlay payouts are calculated

A parlay is a single bet made of several selections, all of which have to win. Because the legs are settled together, the price is not the sum of the individual odds — it is their product, which is why a three-leg parlay at modest prices pays several times the stake.

The arithmetic has three steps, and the calculator above performs all three:

Convert every American price to decimal odds. A favourite at -110 becomes 1.909; an underdog at +150 becomes 2.50.
Multiply the decimals together. Two legs at -110 and one at +150 give 1.909 × 1.909 × 2.50 = 9.112.
Multiply by the stake for the total return, and subtract the stake for the profit. On $100 that is $911.16 back, $811.16 of it profit — the calculator carries the full decimals rather than the rounded 1.909 shown here, which is where the last few cents come from.

Why American odds cannot be added

American odds describe a profit relative to $100, and that reference point changes as the stake rolls over from one leg to the next. Adding -110 and -110 produces a number that means nothing. Decimal odds describe a multiple of the stake, which is exactly the quantity that compounds, so the multiplication is valid. This is the single most common error in a hand-rolled parlay calculation.

What a parlay actually costs

Every leg carries the sportsbook's margin, and a parlay compounds that margin as surely as it compounds the odds. Two legs at -110 each carry about 4.5% of vig; combined, the book's edge on the parlay is noticeably larger than on either bet alone. The implied chance figure in the calculator is what the price says, and the true chance is lower than that.

If you want to see how much of a given price is margin, the implied probability calculator will strip it out of a two-way market. If you want to find the best version of each leg before combining them, compare the posted odds across books first — a half-point of price on every leg compounds too.

A note on same game parlays

This calculator assumes the legs are independent. When two selections come from the same game they usually are not, and multiplying their odds produces a number that is too generous. BestSlip's bet slip detects that case and declines to price it rather than publishing a figure it knows to be wrong; a calculator given nothing but typed prices has no way to tell.