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A parlay, accumulator, or combo bet is a single bet that links together two or more individual wagers and is dependent on all of those wagers winning together. The benefit of the parlay is that there are much higher payoffs than placing each individual bet separately since the difficulty of hitting it is much higher. If any of the bets in the parlay lose, the entire parlay loses. If any of the plays in the parlay ties, or "pushes", the parlay reverts to a lower number of teams with the odds reducing accordingly.^{[1]}^{[citation needed]}
Parlay bets are paid out at odds higher than the typical single game bet, but still below the "true" odds. For instance, a common 2team NFL parlay generally has a payout of 2.6:1 if both picks are correct.^{[citation needed]} In reality, however, if one assumes that each single game bet is a coin flip and would be expected to pay out at 1:1, the true payout should instead be 3:1, a substantial difference.
Mulroe places a threeteam NFL parlay on the Packers, Bears, and Bengals. If any one of those teams fail to cover the spread, Mulroe loses his parlay bet. But if all three teams beat the spread, Mulroe gets paid $600 for every $100 bet.
If Mulroe pushes on one of those picks, he then has a twoteam parlay. If he pushes on two picks, he would then have a straight bet.
Home team  Away team  Home win  Draw  Away win  Result 

Arsenal F.C.  Manchester United F.C.  1.70  3.20  4.50  0–0 (draw) 
Chelsea F.C.  Fulham F.C.  1.70  3.30  4.40  2–1 (home win) 
Liverpool F.C.  Tottenham Hotspur F.C.  1.30  4.00  8.50  3–1 (home win) 
Sam wagers £1,000 on Arsenal/Manchester United to draw, Chelsea to win, and Liverpool to win. Sam wins £6,072 as he correctly predicted all three results.
The calculation is: £1,000 × 3.2 × 1.7 × 1.3 = £7,072, less the stake of £1,000.
Sam wagers £1,000 on Manchester United to win, Chelsea to win, and Liverpool to win. He loses the wager if either Manchester United, Chelsea, or Liverpool loses.
The following is an example of a traditional Las Vegas Parlay Card, which shows the typical payouts for an up to 11 team parlay bet (amount won is assuming $100 is bet):
Number  Odds  Amount won  Payout (if push) 

2 Team Parlay  13 to 5  $260  $360 
3 Team Parlay  6 to 1  $600  $700 
4 Team Parlay  10 to 1  $1,000  $1,100 
5 Team Parlay  20 to 1  $2,000  $2,100 
6 Team Parlay  40 to 1  $4,000  $4,100 
7 Team Parlay  75 to 1  $7,500  $7,600 
8 Team Parlay  150 to 1  $15,000  $15,100 
9 Team Parlay  300 to 1  $30,000  $30,100 
10 Team Parlay  700 to 1  $70,000  $70,100 
11 Team Parlay  1100 to 1  $110,000  $110,100 
Many gamblers have mixed feelings as to whether or not parlays are a wise play. The best way to analyze if they are profitable in the long term is by calculating the expected value. The formula for expected value^{[2]} is: E[X] = x1p1 + x2p2 + x3p3…xkpk . Since the probability of all possible events will add up to 1 this can also be looked at as the weighted average of the event. The table below represents odds.
Column 1 = number of individual bets in the parlay
Column 2 = correct odds of winning with 50% chance of winning each individual bet
Column 3 = odds payout of parlay at the sportsbook
Column 4 = correct odds of winning parlay with 55% chance of winning each individual bet
Number of Individual Bets  Correct Odds at 50%  Odds Payout at sportsbook  Correct odds of winning parlay at 55% 

2  3 to 1  2.6 to 1  2.3 to 1 
3  7 to 1  6 to 1  5.0 to 1 
4  15 to 1  12 to 1  9.9 to 1 
5  31 to 1  24 to 1  18.9 to 1 
6  63 to 1  48 to 1  35.1 to 1 
7  127 to 1  92 to 1  64.7 to 1 
8  255 to 1  176 to 1  118.4 to 1 
9  511 to 1  337 to 1  216.1 to 1 
10  1,023 to 1  645 to 1  393.8 to 1 
11  2,047 to 1  1,233 to 1  716.8 to 1 
The table illustrates that with even a 55% chance of winning each individual bet parlays are still not profitable in the long term. [? no, this table does not illustrate that] Compare this with the expected value you receive on an individual bet with a 55% chance of winning. (.55)(10/11)  (.45)(11/10) = .005 This may not seem like much but it indicates that at even a 55% win ratio every single bet you place will increase your bankroll by .5%. When wagering the ideal amount of money, according to the Kelly criterion, the real amount of money will compound exponentially as your bankroll increases. There are many Kelly calculators available on the internet which illustrate the correct amount of money to wager on any event given the payout and win percentages.