Parlay calculator
A parlay multiplies prices, which also multiplies margins. This page shows both the payout and what the combination costs you.
Build the parlay
This is an assumption you set, not a
figure we publish. 4.55% is the hold on a market with both sides at
-110. Run the vig
calculator on the actual market to replace it with the real number.
- Book pays
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- Book decimal
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- Implied probability
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- Fair price (legs devigged)
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- Fair probability
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- Hold on the parlay
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- EV per unit staked
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- Returns on your stake
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- Same hold, one bet
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What the number means
A standard parlay pays the product of the individual decimal prices. That sounds fair, and the multiplication itself is fair. The problem is that each leg's price already contains a margin, and multiplying prices multiplies the margins with them. Two legs carrying 4.55% hold each produce a parlay carrying about 8.9%; six legs produce about 24%.
That is the whole mechanism, and it is why the same bettor can lose faster
on parlays than on singles without ever making a worse selection. The formula
1 - (1 - h)^n is on the page above so you can see the compounding
directly: change the leg count and watch it move.
The fair price shown here is what the parlay would pay if each leg's margin were stripped out first. The gap between that and what the book pays is the cost of combining.
Where it misleads
This assumes the legs are independent. Correlated legs break the maths completely. A team's moneyline and the game going over, or a quarterback's passing yards and his team covering, move together, and the true joint probability is not the product of the two. Books know which correlations exist, which is why some combinations are blocked and others are priced separately as same-game parlays with their own pricing model. Do not use this page for those.
The hold input is an assumption you supply. If the real markets hold more than you typed, the parlay is worse than shown, and if you enter zero the page will tell you the parlay is fair, because you told it the legs were fair. Garbage in is not detectable by arithmetic.
None of this makes parlays unusable. It makes the cost visible so it can be weighed against whatever you are getting for it.