Updated Sep 7, 2026 · Week 1 board.
What a boost multiplier actually does to the payout
A “25% profit boost” does not add 25% to your stake back. It adds 25% to the profit part of the payout, and that's a different animal. Run it with real money. A $100 ticket at a decimal payout of 7.553 returns $755.34 with no boost, so $655.34 of that is profit.
Boost the same ticket 25% and it returns $919.17, of which $819.17 is profit. Your stake-back dollar never moves. The profit slice is the only thing that grows, by whatever percent the banner advertises, and a 25% boost grows only that slice.
Three real Week 1 favorites, priced and de-vigged
One book, DraftKings, and three home favorites laying their Week 1 spread. Each price below is converted to decimal odds and then to a no-vig fair chance. Fair means what's left after the book's two-sided vig gets pulled out of both sides of that market.
| Leg | Price | Decimal odds | Implied probability | No-vig fair probability | Leg hold |
|---|---|---|---|---|---|
| Seattle Seahawks −3.5 (vs. New England) | −102 | 1.9804 | 50.50% | 48.26% | 4.62% |
| Pittsburgh Steelers −3.5 (vs. Atlanta) | −102 | 1.9804 | 50.50% | 48.26% | 4.62% |
| Philadelphia Eagles −5.5 (vs. Washington) | −108 | 1.9259 | 51.92% | 49.57% | 4.75% |
Leg hold gets figured the standard way. Take both sides' implied chances at the same book, the favorite's price and the underdog price paired with it, add them up, subtract 1. Seattle is −102. New England, the other side of it, is −118.
Those imply 50.50% and 54.13%, which sum to 104.62%, so the hold on that leg is 4.62%. Now the parlay. Multiply the three legs' decimal odds, 1.9804 × 1.9804 × 1.9259, and a $100 stake pays $755.34, of which $655.34 is profit. Multiply the three fair decimals instead, 2.0720 × 2.0720 × 2.0175, and the honest payout is $866.10.
The distance between 7.553 and 8.661 belongs to DraftKings. Same thing from the other direction. The three fair chances multiplied out (48.26% × 48.26% × 49.57% = 11.55%) against what the book's own payout implies (1 / 7.553 = 13.24%) leaves a combined hold of 12.79%. That's nearly triple any single leg's 4.6 to 4.8%.
Vig compounds across legs exactly the way the payout does.
The boost percentage that actually clears the hold
Unboosted, that $100 ticket carries an expected value of −$12.79. An 11.55% true win chance times the $755.34 payout, minus the $100 you put up. Getting back to the fair, no-vig payout takes a 16.9% boost. Under that, the boost is decoration and you're still losing money on this estimate.
Over it, the sign flips.
| Boost | Boosted decimal payout | $100 ticket returns | Expected value on $100 |
|---|---|---|---|
| 0% (no boost) | 7.553 | $755.34 | −$12.79 |
| 25% | 9.192 | $919.17 | +$6.13 |
| 30% | 9.519 | $951.94 | +$9.91 |
| 50% | 10.830 | $1,083.01 | +$25.04 |
So the promo has to clear about 17 points of boost before this exact three-leg ticket stops being a house bet and starts being yours. Anything advertised under that is the same 12.79% hold, and it's wearing a brighter banner.
What the boost table hides
Two things in this math are assumptions, and they should be labeled that way. The “fair” chance is a no-vig estimate taken from one book's own two-sided price. Nobody's verified it against anything. It assumes that book prices efficiently, and that stripping the vig evenly off both sides gets you back to the real number.
If the line is skewed because one side took all the action, the fair estimate comes out skewed with it. The second assumption is independence. The parlay math multiplies the three legs' chances together, and three different games kicking off across three different days are close enough to uncorrelated that it holds up here. It wouldn't hold for legs pulled out of one game.
Same-game parlays are where a boost banner gets furthest from the arithmetic. Check the board before you tap. The live odds page and the odds converter turn any book's American price into the decimal and implied-chance numbers used above. The EV calculator runs the boost break-even on whatever ticket is actually in your slip.
No game above is being recommended. This is the arithmetic a boost promo asks you to do in your head in the two seconds before you tap accept. Check the NFL picks board and the full Week 1 odds desk for the underlying numbers on any specific game.
What the Number Says
12.79% combined hold on three favorites at one book, before a single boost is applied. That is what the ticket costs whether the banner reads 25% or 50%. This one needs roughly 17 points of boost to reach break-even on the no-vig math above, and under that number you're paying for marketing. The boost percent this book actually posts before kickoff settles it.
Watch for it. If it clears 17%, the arithmetic finally sits on your side of the counter.
