Same Game Parlays: The Math Behind Why Books Love Them
How correlated legs are priced, why SGPs almost always have higher hold than independent legs, and when they make sense anyway.
Books love same-game parlays. They run TV ads about them. They feature them in app homepages. They build dedicated SGP construction tools. The reason isn't a love for happy customers. It's that SGPs carry the highest hold of any common bet type at any major U.S. sportsbook. Understanding why is foundational to deciding when an SGP is worth betting and when it's a tax on entertainment.
The basic math of a parlay
A parlay combines multiple independent legs. To compute the combined price, convert each leg to decimal odds, multiply them all together, and convert back to American. Three -110 legs (decimal 1.91 each) combine to roughly 6.97 decimal, or about +597 American. A $100 wager wins about $597 in profit if all three hit.
The implied probability of a 3-leg -110 parlay is about 14.3 percent. The combined hold is the cumulative book edge across all three legs.
Use our parlay calculator to build any combination quickly.
What makes an SGP different
Same-game parlays combine legs within one game. Books price them as correlated, not independent. Take an NBA SGP:
- Lakers -7
- Stephen Curry over 28.5 points
- Game total over 220
If these were independent legs in three separate games, the math would be straightforward multiplication. But they're not independent. If Curry goes over 28.5, the Lakers game is likely high-scoring. If the game is high-scoring, the total is more likely to go over. If the Lakers cover -7, it's plausibly a blowout where pace was high. The legs are positively correlated.
Books recognize this and price the SGP at an implied probability higher than the product of the individual legs would suggest. The "discount" the book gives you (relative to a naive multiplication) is real. The correlation premium the book takes is also real, and it's usually larger than the discount.
Why hold compounds on SGPs
Each leg in a parlay carries the standard book hold. A 3-leg parlay at -110 / -110 / -110 carries roughly 14 to 15 percent cumulative hold. SGPs add a correlation premium on top of that, usually another 5 to 10 percent depending on how correlated the legs are. The total hold on a typical 3-leg SGP at a major U.S. book is often 15 to 25 percent.
For comparison, a 3-leg multi-game parlay (different games) carries roughly 14 to 15 percent hold (just the cumulative individual hold). A single -110 wager carries about 5 percent hold. SGPs are by far the highest-hold bet type a casual bettor encounters regularly.
When SGPs make sense anyway
SGPs aren't always a bad bet. There are two situations where they can have value:
Strong correlation thesis. If you believe two legs are more correlated than the book is pricing them, the SGP can have positive expected value. Example: you think a particular running back is going to dominate a game in a way that correlates with both his rushing yards prop and the spread. If you can articulate why the legs are correlated, and the book's pricing doesn't fully reflect it, the math can work.
Promotional environment. Books frequently boost SGPs as a customer acquisition tool. A 3-leg SGP that originally priced at +400 might be boosted to +500. The boost can move an SGP from negative EV to positive EV, depending on the size. Boosted SGPs are also a typical use case for promotional credits and bonus bets.
Outside these specific cases, SGPs are entertainment, not value. They're priced for the customer who wants the lottery-ticket payout structure and isn't tracking expected value.
How to evaluate an SGP
If you're considering an SGP, do this calculation first:
- Convert each leg to its individual decimal odds.
- Multiply them together to get the naive parlay price (assumes independence).
- Compare to the actual SGP price the book is offering.
- The ratio of book price to naive price tells you how much correlation discount the book is giving (typically 70 to 90 percent of naive).
- Ask yourself whether the legs are correlated enough that the discount is justified, or whether it's overpriced.
If the legs aren't strongly correlated, the SGP is just an expensive way to combine them.
Practical recommendation
For most bettors most of the time, the simplest path is:
- Bet the legs separately at the best available price across books (use MatchupOdds to compare).
- Use SGPs sparingly, only when you have a strong correlation thesis.
- Take advantage of SGP boosts and promotional credits where they exist.
- Don't take SGP suggestions from social media as primary bet decisions.
For more on the underlying math, see our player props guide and vig explainer.
Frequently Asked Questions
Why are same-game parlays priced so unfavorably?
Books price SGP legs as correlated. The math accounts for shared dependencies (e.g., a high-scoring game tends to have over hits and high-yard QB props). The correlation premium plus the standard hold makes SGP hold often exceed 15 percent.
Are SGPs ever good bets?
Yes, when you have a strong correlated thesis (e.g., a player's prop is correlated with a team result and the SGP price prices the legs as roughly independent). They are rarely good as a default bet type for value.
How is an SGP different from a multi-game parlay?
A multi-game parlay combines independent events (different games), so the math is the simple multiplication of decimal odds. An SGP combines events within one game, which are correlated, so the book applies a correlation discount.
Should I bet SGPs from social media slips?
No. The picks usually come from accounts whose business model is engagement, not value. The expected EV of a typical 5-leg SGP is deeply negative.