The Line · Execution
A parlay is priced by multiplying its legs together — which means the bookmaker's margin multiplies too. A typical single bet holds about 4.5%. Four of them parlayed holds 16.8%. Your bet slip will not tell you that.
Enter both sides of each leg — the price you are taking, and the price on the other side of the same market. Both are on your bet slip screen, and the second one is what makes the fair price computable.
This pays +264. Stripped of the margin on each leg it is worth +300 — so 8.9% of what the bet is worth never reaches you.
That is the compounding: a margin of a few percent on each of 2 legs multiplies rather than averages. A typical 2-leg parlay at standard prices holds about 8.8%.
On a $20 stake the margin alone costs about $1.78 per bet, or $178 over a hundred of them. Arithmetic on the margin — not a prediction of how you will actually do.
A single price cannot be de-vigged. −110 tells you what the book is charging, not what the outcome is worth — the fair number only appears once you can see both sides and normalise them so they add to 100%. That is why the calculator asks for the opposing price, and why it refuses to produce a fair price when a leg is missing one.
We could assume a typical margin for the missing leg. The number would look authoritative and it would be made up, and it would err in the book's favour by exactly the legs we skipped. Everything we publish and every model we have killed is on /receipts, for the same reason.
It is not a recommendation to place this parlay, or to place a different one, or to place none. We do not sell picks — two pre-registered backtests found us no edge on NFL games, and we publish those too. This is the price tag, printed.