A parlay, called an accumulator or “acca” in the UK, links two or more bets into one wager, and every leg must win for the bet to pay. The payout multiplies the odds of each leg, so it grows fast, but the sportsbook’s margin multiplies as well. At standard -110 prices a two-leg parlay costs you about 8.9% of your stake on average, against 4.5% for a single bet, and a ten-leg parlay costs about 37%.
This guide shows exactly how a parlay is priced, why the cost climbs with every leg you add, what correlation and same-game parlays change, and what happens when a leg is voided. The edge figures are our own calculation from the odds, and the working is shown so you can check it.
What is a parlay, and how does it work?
A parlay is a single bet made of several selections, called legs. You win only if all legs win. If one leg loses, the whole bet loses, even if every other leg was right.
The odds are multiplied together. In decimal odds, a 1.909 leg and another 1.909 leg combine to 1.909 x 1.909 = 3.645, so a $100 stake returns $364.50 if both win, a profit of $264.50. American odds of -110 are the same price as decimal 1.909, so this is the standard two-leg parlay that pays about 2.64 to 1.
Three more terms matter:
- Leg: one selection inside the parlay, such as a team to win or a game total.
- Push: a leg that ties the line. It is removed and the parlay continues with fewer legs at adjusted odds.
- Round robin: a set of smaller parlays built from a larger list of picks, so one miss does not kill every bet.
Parlays are offered across sports, and in the UK the same bet is the accumulator. The price table in the next section applies to both names.
How much does a parlay cost compared with a single bet?
Every leg carries the sportsbook’s margin, and the margin compounds across legs. A single bet at -110 on each side has a built-in cost of about 4.55%. A parlay multiplies the payout by the same shortfall on every leg.
Here is the calculation, step by step. A -110 price pays $0.909 profit per $1 staked, or a decimal 1.909. If a leg truly has a 50% chance, its fair price would be decimal 2.00. Each leg therefore keeps 1.909 / 2.00 = 95.45% of its fair value. For n legs the average return per $1 is 0.9545 raised to the power n, and the cost is one minus that number.
| Legs | Parlay pays (to 1) | Fair price if every leg is 50% | Chance all legs win | Average cost of the stake |
|---|---|---|---|---|
| 1 | 0.91 | 1 | 50.0% | 4.55% |
| 2 | 2.64 | 3 | 25.0% | 8.88% |
| 3 | 5.96 | 7 | 12.5% | 13.03% |
| 4 | 12.28 | 15 | 6.25% | 16.98% |
| 5 | 24.36 | 31 | 3.13% | 20.75% |
| 6 | 47.41 | 63 | 1.56% | 24.36% |
| 8 | 175.45 | 255 | 0.39% | 31.08% |
| 10 | 642.08 | 1,023 | 0.10% | 37.20% |
Put in money, ten $10 single bets cost you about $4.55 in total over time. One $10 five-leg parlay costs about $2.08 per bet, which sounds smaller but is not: a $10 stake on the parlay loses 20.75% on average, against 4.55% on a $10 single bet. The cost per dollar staked is what counts.
Why does a parlay break even only at 52.38% per leg?
The break-even win rate for every leg of a standard parlay is 52.38%, however many legs you add. That is 1 divided by 1.909. A bettor who truly wins 52.38% of -110 legs breaks even on singles and parlays alike.
The parlay does not change that number. What it does is raise the cost of being wrong, and make winning rare. At a true 50% per leg, a five-leg parlay wins 3.13% of the time, or about once in 32 tries. The big payout of 24.36 to 1 is paid to the rare winner, while the other 31 tickets lose.
If a bettor really could win 55% of legs, the maths turns in their favor, because 0.55 x 1.909 = 1.05 per leg and 1.05 compounded over ten legs is 1.63. That is a 63% average profit. The hard part is the premise. A 55% win rate on -110 bets means beating the posted price by 2.6 points on every leg, and the price already reflects the sportsbook’s own estimate of each game.
Why do sportsbooks promote parlays so much?
Parlays give the sportsbook a larger margin per dollar and make wins look easy. A bettor who sees “turn $10 into $500” is looking at the rare tail of the table above, not the typical result.
There is also a psychological effect. Near misses, such as winning four legs of a five-leg parlay, feel like almost winning. They are still full losses. Our guide to how gambling games hold your attention explains why near misses pull people back to bet again.
What is correlation, and what are same-game parlays?
Correlation means the legs are not independent. If one leg wins, the chance that another wins moves with it. A team to win and the total goals to go over, in the same football match, are an example: a high-scoring game makes both more likely.
The simple multiplication in the table assumes independent legs. For correlated legs, the true chance of all legs winning is different from the product of the individual chances. Traditional bookmakers often refuse to combine correlated selections for that reason. Same-game parlays let you combine several selections from one game, and the sportsbook adjusts the price for the link. The price you see is the sportsbook’s own estimate, and you cannot check the margin built into it the way you can with independent legs at a known price.
The practical rule is simple. Treat a same-game parlay as a single bet with an unknown margin, and assume the margin could be as large as for an ordinary parlay of the same length, or larger.
How can you check a parlay price yourself?
You can check any parlay in four steps, using decimal odds. This takes a minute and shows whether a boosted price is really a good one.
- Convert each leg to decimal. For a negative American price, decimal = 100 divided by the price (ignoring the minus) plus 1. For a positive price, decimal = price divided by 100 plus 1.
- Multiply the decimals. The product is the total return per $1, including your stake.
- Turn each leg into an implied probability. That is 1 divided by its decimal odds.
- Multiply the probabilities. The result is the chance the price needs for the parlay to break even.
A worked example: take a -150 favorite (decimal 1.667), a +120 underdog (decimal 2.20) and a -110 side (decimal 1.909). The product is 1.667 x 2.20 x 1.909 = 7.00, so a $10 stake returns $70, a profit of $60. The implied probabilities are 60.0%, 45.5% and 52.4%, and their product is 14.3%. If you believe all three legs together win more often than 14.3% of the time, the price is worth taking. If you believe they win less often, it is not, and the margin on each leg is working against you.
What is a round robin?
A round robin splits a list of picks into several smaller parlays. With four picks, a “by 2s” round robin makes every possible two-leg parlay, which is six bets. It is a different way to spread risk, not a way to remove cost. Each of the six bets carries the two-leg cost of 8.88% in our table, and you stake six units instead of one. If you win three of the four picks, only the three two-leg parlays made from your winners pay out. The total cost of the round robin is the same average percentage as the two-leg parlays inside it.
What happens if a leg is voided, pushed or cancelled?
A pushed or voided leg is removed and the parlay continues with fewer legs at adjusted odds. New Jersey’s patron wagers rule gives a clear example from a regulator: if a leg is a prohibited event, the wager stands and the event is removed as if it were never part of the bet, so a six-leg parlay with one prohibited leg becomes a five-leg parlay.
The same rule says an operator may not rescind a wager without approval from the regulator, and that wagers made after an outcome was known are voided. Other places have their own rules, so read the sportsbook’s published settlement terms before you bet.
What are the most common parlay mistakes?
The mistakes come from underestimating the cost of each added leg. The usual ones:
- Adding “one more leg” for a bigger payout. The cost rises with every leg, as the table shows.
- Counting favorites as safe. A -300 favorite wins about 75% of the time at the price, and four of them together win about 32%.
- Betting parlays with money you cannot afford to lose. Most parlays lose, by design.
- Chasing a near miss. A four-of-five loss is a loss, not a sign the next one will hit.
- Using boosts without checking the maths. A “boosted” payout may still be below the fair price once you multiply the true chances.
What does a parlay cost over a season?
The cost is the average loss per dollar times the total you stake. A bettor who places 50 five-leg parlays at $10 each stakes $500 and, at the table’s 20.75% cost, expects to lose about $104. The same $500 spread over 50 single bets at 4.55% costs about $23.
These are averages. A small number of winning tickets can pay for many losers, so a single month can look very different. Decide how much you can spend before you bet, and stop when you reach it. Our guide to setting a gambling budget and time limit shows how, and the Safer play toolkit lists tools and support. If betting is causing harm, visit our get help page.
Sports betting is legal in some places and not in others. See is gambling legal where you live and US gambling law before you place a bet.
Where should you go next?
Learn how a single price turns into a probability in probability and odds in plain language. Then read football betting basics for the markets that parlays are most often built from, and how horse racing betting works for a different system where the odds come from a shared pool.