Free tool
Implied probability calculator
Convert any American odds, or a prediction-market price, into the win probability baked into the line, then enter your own estimate to see whether there's genuine value in the bet.
Implied probability calculator
e.g. -110, +150
Kalshi / Polymarket price (overrides odds)
Optional, calculates your edge
What the book thinks your odds of winning are
What the odds should be without the book's cut
A −110 line implies 52.4%, but the vig inflates it. A prediction-market price sits closer to the true probability.
How to read the output
Enter the odds (or a prediction-market cents price) and the tool returns the implied probability and the fair, no-vig price. Add your own win estimate and it shows your edge: positive means the bet has value at that price.
Why implied probability beats the raw odds
The odds hide the book's cut. A -110 line implies 52.4%, but both sides of a -110/-110 market add to about 105%, and that extra 5% is the vig. Stripping it out tells you the price you'd actually need to be a long-term winner.
Frequently asked
What is implied probability in sports betting?
Implied probability is the win chance built into the odds by the sportsbook, including the vig. A -110 line implies a 52.4% win chance. If you believe the true probability is higher, there's positive expected value in the bet.
Do prediction markets like Kalshi and Polymarket have vig?
Far less than a sportsbook. A -110 line carries about 4.5% vig baked into the price, so its implied probability is inflated. A prediction-market price sits much closer to the true probability.
More tools
No-vig calculator →
Strip the sportsbook's vig out of any two-way line to get the fair odds and the true, de-juiced win probability for each side.
Odds converter →
Convert between American, decimal, and fractional odds, plus Kalshi and Polymarket prediction-market prices.
Kelly criterion →
Find the mathematically optimal bet size from your edge and bankroll.