What is implied probability in betting?

The chance of an outcome according to its price. Convert the odds to decimal and divide one by the result: -110 is 1.909 in decimal, so it implies 52.38%. It is what the sportsbook's price says, not what will happen.

Why do both sides of a market add up to more than 100%?

Because the sportsbook builds its margin into both prices. Two sides at -110 imply 52.38% each for a total of 104.76%. That 4.76 points is the vig — the book's expected revenue regardless of which side wins.

How do you remove the vig from betting odds?

Add up the implied probabilities of every outcome, then divide each one by that total. Two sides at -110 each become 52.38 / 104.76 = 50.0%. This proportional method is the standard approach and assumes the book spread its margin evenly across the outcomes.

Is the no-vig price the true probability?

No. It is the market's opinion with the margin stripped out, which is a much better estimate than the raw price but still only an estimate. It is most useful as a comparison: a no-vig price from a sharp book is a reasonable benchmark for the same outcome elsewhere.

Free calculator

Implied Probability Calculator

Turn a posted price into the probability it implies, then remove the sportsbook's margin to see what each side of the market is really priced at.

The market

Every outcome, in American odds

Side A

52.38%

Implied

50.00%

No-vig

Side B

52.38%

Implied

50.00%

No-vig

Three outcomes for a market that can draw

The book's margin

Market total: 104.76%
Vig: 4.55%
Side A fair price: +100
Side B fair price: +100

Posted prices always add up to more than 100%. The excess is the sportsbook's margin, and removing it proportionally is what makes two books' prices on the same outcome comparable.

Frequently asked questions

What is implied probability in betting?: The chance of an outcome according to its price. Convert the odds to decimal and divide one by the result: -110 is 1.909 in decimal, so it implies 52.38%. It is what the sportsbook's price says, not what will happen.
Why do both sides of a market add up to more than 100%?: Because the sportsbook builds its margin into both prices. Two sides at -110 imply 52.38% each for a total of 104.76%. That 4.76 points is the vig — the book's expected revenue regardless of which side wins.
How do you remove the vig from betting odds?: Add up the implied probabilities of every outcome, then divide each one by that total. Two sides at -110 each become 52.38 / 104.76 = 50.0%. This proportional method is the standard approach and assumes the book spread its margin evenly across the outcomes.
Is the no-vig price the true probability?: No. It is the market's opinion with the margin stripped out, which is a much better estimate than the raw price but still only an estimate. It is most useful as a comparison: a no-vig price from a sharp book is a reasonable benchmark for the same outcome elsewhere.

What implied probability is

Every price is a statement about how likely an outcome is. Convert the odds to decimal and divide one by the result, and you have that statement as a percentage. A favourite at -250 is 1.40 in decimal, which implies 71.43%; an underdog at +200 is 3.00, which implies 33.33%.

Those two add up to 104.76%, which is the first thing worth noticing about implied probability: it is never only probability.

Where the extra percent comes from

A sportsbook that priced a coin flip honestly would post both sides at +100 and make nothing. Instead it posts both at -110, and the 4.76 points of excess — the overround, the juice, the vig — is its margin. It is charged on both sides, so the book collects it whichever way the game goes.

This is why a bettor winning exactly half their -110 bets loses money: at 52.38% implied, you need to win 52.38% of the time just to break even.

How removing the vig works

The calculator uses the proportional method, which is the standard one. Add up the implied probabilities of every outcome, then divide each by that total so they sum to exactly 100%:

Outcome	Posted price	Implied	No-vig
Side A	-250	71.43%	68.19%
Side B	+200	33.33%	31.81%
Total	—	104.76%	100.00%

Worth being honest about the assumption: this spreads the margin evenly across the outcomes, and real books usually load more of it onto the longshot. Other methods exist that try to model that, and all of them need assumptions of their own. The proportional version has the advantage of being transparent about its arithmetic.

What to do with the number

The no-vig price is a benchmark. If one book's fair number for an outcome is 68% and another book is offering a price that implies 64%, the second price is the better bet according to the first book's own opinion. That comparison is the entire reason to shop lines across sportsbooks rather than taking whichever price is in front of you.