Half Point Calculator
Buying half a point moves the line your way and the book charges you for it. This is what the move is actually worth.
Your spread sits on a key number, so this is the expensive half point. Buying it moves the implied price from 52.38% to 61.88% — 9.50 points of win probability. It only pays if the book charges you less than that to move the line.
Buying the half point is cheap insurance. Take it every time.
The line
What the price says now
That is how much win probability one half point carries at this number. It is the whole question: everything below is that figure added to or taken off the price you already have.
Buying the half point
The fair price is what the book would have to charge for the better number to break even on the swap. Pay more than that and you have bought the point at a loss.
Selling the half point
Selling is the same trade run backwards: you take the worse number and the book pays you in price. Take less than the fair figure above and you have sold the point cheap.
What a half point is worth by NFL margin
Three and seven are the margins NFL games land on most, which is why the half points that cross them move the price furthest. Anywhere else on the board the same half point barely touches the game, and the book still wants paying for it. Spreads outside this table use the league default.
These half point values are league averages, not this game's. A low-total defensive struggle and a shootout do not land on the same margins, and a book will rarely sell you a key number at the price it sells the ones either side of it. This page prices the move. It cannot see what the counter is charging you for it, so bring that number yourself and compare.