No-vig calculator
Enter the two prices a sportsbook is offering on the same market and the calculator strips the book's margin out — the fair odds underneath.
Enter two American prices
Fair odds
| Side | Implied | Fair % | Fair odds |
|---|---|---|---|
| Over / A | — | — | — |
| Under / B | — | — | — |
- Total implied
- —
- Vig
- —
The calculation runs in your browser. Nothing you type is sent anywhere.
What the vig actually is
A sportsbook does not post the probability it believes in. It posts a price with its margin already inside, and that margin is the vig — also called the juice, the overround or the hold. It is the reason a genuine coin flip is priced at -110 on both sides instead of +100 on both sides.
Work the standard example through. A -110 price implies a 52.38% chance. Both sides of a -110/-110 market imply 52.38%, so the two add up to 104.76% — and a real market cannot add up to more than 100%. That extra 4.76% is the vig. Divide each side by 104.76% and you get 50% and 50%, which converts back to +100 and +100. Those are the fair odds.
That is the whole job of a no-vig calculator: convert both prices to implied probability, remove the excess, and convert what is left back into odds. Fair odds are what you compare a bet against. If a book is offering you better than the fair number on the same outcome, the bet has positive expected value; if it is offering worse, you are paying the margin.
Multiplicative or additive
The two methods agree on an even market and disagree on a lopsided one, which is exactly when it matters. The multiplicative method divides each side by the total, so it removes the margin in proportion — the heavy favourite gives back more of it. The additive method splits the excess evenly and subtracts the same amount from each side, so the underdog gives back proportionally more.
Neither is correct in an absolute sense. Most bettors use multiplicative as the default and check additive when the market is heavily one-sided, because the gap between the two answers is a fair measure of how much the de-vig itself is guessing.
The shortcut: a price that has no vig in it
De-vigging a sportsbook line is an estimate of fair value built from a number that has been deliberately shaded. A prediction market quote is not: on Kalshi, Polymarket or Novig the price comes from traders on both sides and the fee sits outside the price, so a 42¢ contract is already close to a 42% probability with nothing to strip out.
That makes the two families of number worth putting side by side. De-vig the book here, then look at what an exchange is charging for the same outcome — if the exchange is cheaper, the book's fair price was not fair enough.
One disambiguation, because the names collide: no-vig is the arithmetic on this page. Novig is a peer-to-peer exchange BeatVig prices. They are not the same thing, and this calculator works on any venue's prices.
No-vig calculator FAQ
What is a no-vig calculator?
A no-vig calculator removes a sportsbook's built-in margin from a two-sided market and returns the fair odds underneath. It converts both posted prices to implied probability, scales them so they add up to 100%, and converts the result back to American odds.
How do you calculate no-vig odds?
Convert each American price to an implied probability, add the two probabilities together, then divide each one by that total so they sum to 100%. Converting those adjusted probabilities back to American odds gives the no-vig fair odds.
What is the difference between vig and hold?
Vig is the excess in a market's implied probabilities above 100%, so -110/-110 carries 4.76% of vig. Hold is the share of total handle a book expects to keep, which on that same market is 4.55%, because the excess is measured against the larger total rather than against 100%.
Can I use a no-vig calculator on player props?
Yes, and props are where it matters most, because prop markets usually carry more vig than sides and totals. Enter the over price and the under price on the same line and the calculator returns the fair number for each side.
Do prediction market prices need to be de-vigged?
Not in the same way. Kalshi, Polymarket and Novig quote a contract that settles at $1, and their fee is charged separately rather than being built into the quote, so the price is already close to an implied probability.
What are fair odds in sports betting?
Fair odds are the price a market would offer if it took no margin at all, which is the break-even number for a bet. A price better than fair odds carries positive expected value and a price worse than fair odds is paying the book's margin.