Parlays and Why the Math Turns Against You

Q: Why do parlays favor the sportsbook so much?

Because the house's cut multiplies across every leg instead of just adding up. A single -110 bet gives up about 4.5%; a 6-leg -110 parlay gives up about 24.2%.

Q: Are parlays worth betting?

They're fine as a fun, small bet, but not as a strategy. They're not part of how a real edge is found and shouldn't be a real part of a bankroll.

Q: How are parlay odds calculated?

Convert each leg to decimal odds, multiply those decimal prices, then convert the product back to the displayed format. The calculation assumes every leg must win.

Q: Why are correlated parlay legs different?

Correlated outcomes are not independent, so multiplying their standalone probabilities can misprice the ticket. Sportsbooks may restrict the combination or adjust the payout to account for that relationship.

Quick answer

A parlay strings multiple bets into one ticket where every leg must hit. The sportsbook's cut compounds with each added leg, a 6-leg parlay of -110 bets keeps close to 24% of the fair payout. Fun for a fun bet, not a strategy.

What a parlay is

A few bets glued into one ticket. Every leg has to hit or the whole thing's dead, no matter how the rest went. In exchange, the payout looks huge, because you're getting paid for something a lot harder to pull off.

The cut doesn't add up, it stacks

A single -110 bet already gives up about 4.5% to the house. You'd think a 3-leg parlay carries that same small cut. It doesn't, each leg's price multiplies into the next, and so does the house's cut on each one.

-110 legs, stacked together

Legs	Fair payout	Book pays	Real cut
1	2.00×	1.91×	4.5%
3	8.00×	6.96×	12.9%
6	64.00×	48.51×	24.2%

Same -110 price every leg. Stack six of them and the house is keeping almost a quarter of what a fair payout should be.

About those huge parlay wins you see online

A 6-leg parlay of coin-flip-strength bets hits about 1 time in 60. Nobody posts the other 59 losing tickets, so all you ever see is the rare one that hit. That's not a system working. That's a lot of people trying and a few getting lucky.

Bottom line

Throw a few bucks on a big parlay for fun during a game, sure, that's what it's there for. Just don't mistake it for a strategy. It's not part of how we find edges, and it shouldn't be a real part of your bankroll either.

Parlays: frequently asked questions

Why do parlays favor the sportsbook so much?

Every leg carries a margin and every leg must win. As the prices multiply, those small disadvantages compound into a much larger gap between the fair payout and the offered payout.

Are parlays worth betting?

They can be entertainment if the stake is deliberately small, but a large headline payout is not evidence of value. Judge the price and probability of the entire ticket, not the excitement of its possible return.

How are parlay odds calculated?

Convert each leg to decimal odds and multiply them. Three legs priced at 1.91 decimal each produce about 6.97 decimal before any sportsbook-specific adjustment. The winning probability moves the opposite way: multiply the estimated probability of each independent leg.

Why are correlated parlay legs different?

Some outcomes affect each other. A quarterback passing over and his receiver gaining over may be positively correlated, so treating them as independent can overstate the fair payout. Books may block the pair or reprice it. Correlation can also be negative, and it must be modeled rather than assumed.