How to Bet Same-Game Parlays: Fair Odds, Correlation and Bonuses

Same-game parlays are the most popular bet in football, and for most people the worst one. Not because they never hit (they do), but because the price is usually lower than the bet is worth. The good news: it's easy to check. Five steps, one calculator, and you'll know whether a slip is worth it before you tap "place bet".

We'll use a real ticket as the example: our Thursday Night Anti-Boom Special, a three-leg Steelers-Browns parlay we placed at DraftKings.

Why most parlays lose#

Every price at a sportsbook carries a small tax, the vig. A normal −110 bet needs to win 52.4% of the time to break even. If it's really a coin flip, you lose about 4.5 cents for every dollar you bet.

A parlay multiplies that tax, leg by leg:

| Bet | Pays | Fair price if each leg is 50% | Your average loss per $1 | |---|---|---|---| | One leg at −110 | −110 | +100 | 4.5¢ | | Two legs at −110 | +264 | +300 | 8.9¢ | | Three legs at −110 | +596 | +700 | 13.0¢ |

That's the whole business model. The more legs, the bigger the book's cut, and the payout looks exciting enough that nobody checks.

Step 1: Turn every price into a percentage#

Odds are a percentage in disguise: they tell you how often the book thinks something happens.

• Minus odds: divide the odds by the odds plus 100. −146 → 146 ÷ 246 = 59.3%.
• Plus odds: divide 100 by the odds plus 100. +375 → 100 ÷ 475 = 21.1%.

Our three legs, as the book priced them:

| Leg | Odds | The book says | |---|---|---| | Browns +3.5 | −146 | 59.3% | | Deshaun Watson under 187.5 passing yards | −112 | 52.8% | | Jaylen Warren under 67.5 rushing yards | −114 | 53.3% |

Step 2: Get your own number for each leg#

This is the hard part, and the part most bettors skip. You need your own chance for each leg, from something other than the odds.

Here's where ours came from:

• Watson under 187.5: we project him for 162 passing yards, which makes the under about 66%. Every player's chance at every line is on Boom Yards.
• Warren under 67.5: we project 61 rushing yards, about 64%. Pittsburgh throws on 66% of its plays, second-most in the NFL, so fewer carries go to running backs.
• Browns +3.5: our projected spread has Cleveland winning by about a point (Boom Matchups), and in games with totals this low, a two- or three-point favorite fails to cover +3.5 about 62% of the time. We call it 61%.

Where our number beats the book's, the leg is value: the price pays more than it's worth. All three legs here were value on their own.

Step 3: Multiply, then think about correlation#

Multiply the three chances: 61% × 65.5% × 63.5% = 25.4%. As odds, that's +294. That's our fair price for the parlay.

Now the catch with same-game parlays: the legs aren't independent. An ugly, low-scoring game makes all three more likely at once. When one hits, the others tend to come with it. So the real chance is a bit higher than the straight multiplication, probably 27% to 29% here.

The book knows this too. Multiply the three prices and the parlay would pay about +499. DraftKings paid +375, because it charges you for the correlation. That's the second tax on SGPs, and it's why "they all go together" isn't automatically an edge. It's already in the price.

Step 4: Compare your price with theirs#

You now have two numbers: the chance it hits (ours: 25.4%) and what it pays (+375). Expected value tells you what the bet is worth on average:

EV = your chance × the decimal odds − 1

+375 is 4.75 in decimal odds, so: 0.254 × 4.75 − 1 = +0.21. On our numbers, every dollar on this ticket is worth about 21 cents of profit on average. That's rare for a parlay, and it happened because all three legs were value on their own.

Most of the time you'll do this and find a negative number. That's the point: now you know before you bet.

Step 5: Bonus first#

A profit boost changes what the bet pays, so it changes everything above. DraftKings had a 50% same-game parlay profit boost on this game (three or more legs, +300 minimum, up to a $250 bet). It boosts the profit, not the stake:

• +375 means $3.75 profit per $1. Boosted 50%: $5.63. The ticket now pays +563.
• At +563 the break-even drops from 21.1% to 15.1%.
• EV at our 25.4%: 0.254 × 6.63 − 1 = +0.68, or 68 cents per dollar.

Here's why we only play same-game parlays with a bonus. Suppose we're wrong about Watson and the market is right that his under is closer to a coin flip. Then the parlay is about 20.5% to hit. Straight up at +375, that's roughly break-even (−3 cents per dollar). With the boost, it's still +36 cents per dollar. The boost is the edge either way. Our read on the legs only decides how big.

The checklist#

1. Price every leg as a percentage. If you can't get your own number for a leg, you're guessing.
2. Fewer legs. Every leg adds the vig again. Two or three good legs beat six hopeful ones.
3. Correlation is usually priced in. Don't pay extra for legs that "go together" unless each is value alone.
4. Bonus first, then better legs. A boost can turn a fair bet into a good one. Save boosts for bets you'd make anyway.
5. Size it for losing. Even a +68¢ bet loses three times out of four at 25%. We bet one unit.
6. Check your book's cash-out terms before you cash out a boosted bet. On many books, the cash-out offer ignores the boost.

For the promos themselves (profit boosts, bonus bets, bet-and-gets), see what each sportsbook promo is really worth.