One ticket, every pick must win
A parlay (called an “accumulator” in much of the world) combines two or more picks into a single ticket. Every leg has to win. One loss, or one push, depending on the book’s rules, and the whole ticket is gone.
The appeal is obvious: a small stake can turn into a big payout. Two legs at -110 pay about +264; four pay more than +1,200. The trade-off is just as real: the more legs you add, the less often the ticket wins, and the book’s margin compounds with every leg. This guide covers how the math works, how same game parlays are priced differently, and what teasers and round robins actually are, with the arithmetic up front and no hype.
How the odds multiply
A standard parlay’s odds come from multiplying the decimal odds of each leg, then converting the result back to American. (New to the formats? Our guide to how betting odds work covers the conversions.)
Worked example: two legs at -110 each.
- Convert each leg to decimal: -110 → 100 ÷ 110 + 1 = 1.909.
- Multiply: 1.909 × 1.909 = 3.645.
- Convert back to American: (3.645 − 1) × 100 = +264.5 (the full-precision figure is +264.46, which books typically show as +264).
So a $100 two-leg parlay returns $364.46 if both legs win. For comparison, the same $100 split into two $50 singles returns $190.91 if both win: the parlay pays nearly twice as much, because it also fails whenever either leg fails.
Simple illustration: two legs at +100 (even money) multiply to 2.00 × 2.00 = 4.00, which is +300. Three +100 legs: 2.00 × 2.00 × 2.00 = 8.00, or +700. The multiplication works the same at every size; only the number of legs changes.
A note on rounding: books may round the final price slightly, and each leg carries its own exact price, a -105 leg and a -115 leg each convert to their own decimal before multiplying. The principle never changes: convert to decimal, multiply, convert back.
The honest math on hit rates
Here’s where parlays earn their reputation. If every leg is priced like a coin flip, -110, an implied 52.4%, then the implied probability of the full ticket is those percentages multiplied:
| Legs | Example payout | Implied hit rate |
|---|---|---|
| 2 | +264 | 27.4% |
| 3 | +596 | 14.4% |
| 4 | +1,228 | 7.5% |
| 5 | +2,436 | 3.9% |
Read the table as a warning and a promise at the same time. A four-leg parlay at these prices pays more than twelve times your stake, and lands roughly once in thirteen attempts. That’s the deal, stated honestly: the payout is big because the probability is small.
There’s a second layer most bettors never see: the margin compounds too. A single -110 bet, if the true chance is 50%, carries about 4.5% of margin. Two legs: about 8.9%, roughly $9 of every $100 staked. Three legs: about 13%. Four: about 17%. Each leg multiplies the book’s edge along with your odds, because each leg is priced a little worse than fair and those discounts stack.
None of this makes parlays “bad.” It makes them what they are: an entertainment product with a steeper price than singles, sold on the excitement of the long shot. If you play them, play them for fun and keep the stakes small relative to your bankroll. If your goal is grinding value, singles are the cleaner vehicle.
Same game parlays: same idea, different pricing
A same game parlay (SGP) takes every leg from one game. A standard parlay’s legs come from different games. The difference sounds cosmetic; the pricing is not.
When legs come from different games, treating them as independent is reasonable, and multiplying prices is roughly fair. When legs come from the same game, outcomes are correlated, and multiplying assumes they aren’t. Books price SGPs with a correlation model, so the number on your slip is not simply the product of the legs.
Positive correlation: legs that tend to happen together. A favorite covering -7.5 and the game going over 48.5: blowouts usually mean points, so if one happens, the other is more likely. Same for a quarterback’s passing yards over and his top receiver’s receiving yards over. Because the outcomes co-occur more often than independence suggests, the fair price is shorter than naive multiplication, and books do price SGPs shorter than multiplying the legs would suggest. If multiplying two legs gives +264, a positively correlated SGP will often pay less than that. That’s not a trick; it’s the correlation being priced.
Negative correlation: legs that pull against each other. A game under 44.5 and one team’s team total over 27.5: the more one team scores, the harder the under gets. Here the true joint probability is lower than the product, so the fair price would be longer. Books still build in margin, so don’t assume you’ll see a bonus, but the direction of the adjustment is real.
Practical upshot: sportsbooks curate which legs can go into an SGP and price each combination themselves; some combinations are blocked entirely. The quoted SGP price is the only price that matters. Don’t build an SGP expecting the math from the standard parlay section to hold, it won’t, by design.
Teasers and round robins, briefly
Two parlay cousins you’ll see on the menu:
Teasers let you move the line in your favor, typically 6 or 6.5 points on football spreads and totals, in exchange for worse odds. Example: a teaser moves a -7.5 spread to -1.5 and a total of 48.5 down to 42.5. Both legs still have to win, but a two-leg 6-point teaser commonly pays around -120 instead of -110. You bought points; the book charged you in price. Teasers aren’t a loophole: the points you gain and the odds you give up are balanced by the book’s model. They’re most common in football, and not every sport or book offers them.
Round robins turn a set of picks into multiple smaller parlays instead of one big one. Three picks played “by twos” become three separate two-leg parlays; four picks by twos become six; four picks by threes become four. If two of your three picks win in a by-twos round robin, one of the three parlays cashes. Each combination is its own stake, though, a three-pick round robin by twos costs three times a single parlay. More coverage, more total risk.
Should you build parlays?
An honest summary:
- Parlays multiply your odds and the book’s margin at the same time. The bigger the payout, the rarer the win, by exactly that math.
- Same game parlays are priced by correlation, not multiplication. Check the quoted price; that’s the real number.
- Teasers and round robins are variations on the same trade: more legs, more conditions, more margin.
- No combination of picks changes the underlying probabilities. The math is the math.
If a big payout is part of why you enjoy betting, parlays deliver that, and there’s nothing wrong with a small-stake ticket on a Sunday. Just go in knowing the hit rate you’re buying. If you want the full odds picture first, start with how betting odds work; if you’re still deciding between bet types, see moneyline, spread and totals explained. Our glossary covers parlay, same game parlay, teaser and round robin in one line each.
The short version
A parlay is a trade: a bigger payout for a much smaller chance. Standard parlays multiply decimal odds; same game parlays are priced with correlation in mind; teasers buy points with worse odds; round robins cover combinations for more stake. The table above is the honest version of the pitch: +264 is a 27.4% shot, +1,228 is a 7.5% shot, and nothing changes that except the legs you pick. Choose accordingly.
