Implied probability is the chance of an outcome that a given price or set of odds is quietly expressing. It is the bridge between the number you see on screen and the real-world likelihood of an event — and once you can read it, every market becomes easier to judge. This is the practical companion to why a price equals a probability, which explains why the two line up; here we focus on how to read and convert it.
What implied probability is
Any price that pays out on a yes/no outcome can be restated as a percentage chance. In a prediction market this is unusually direct: contracts settle at $1 if the event happens and $0 if it does not, so a contract’s price is its implied probability, near enough. A contract trading at 62¢ implies roughly a 62% chance; one at 8¢ implies about 8%. Sportsbook and traditional betting odds express the same idea less transparently, which is why converting them into a percentage is such a useful habit.
Reading a contract price
For an event contract, the maths is almost trivial: divide the price in cents by 100. A price of 40¢ is a 40% implied probability; 75¢ is 75%. Your potential profit is the gap between what you pay and the $1 settlement — buy at 40¢ and a winning contract returns 60¢ of profit on 40¢ risked. That clean relationship between price, probability and payout is the whole appeal of the format, and it is why the profit calculator can turn any price and stake into a payout in one step.
Converting odds formats
Elsewhere you will meet the same probability dressed as decimal, fractional or American odds. The conversions to an implied percentage are:
- Decimal — divide 1 by the decimal odds. Odds of 2.50 imply 1 ÷ 2.50 = 40%.
- Fractional — divide the denominator by the sum of both numbers. Odds of 3/2 imply 2 ÷ (3 + 2) = 40%.
- American, positive — 100 ÷ (odds + 100). A line of +150 implies 100 ÷ 250 = 40%.
- American, negative — the absolute odds ÷ (that value + 100). A line of −200 implies 200 ÷ 300 = 66.7%.
You do not have to do this by hand — the odds converter moves between contract cents, decimal, fractional, American and implied percentage instantly. But knowing the formulas means you always understand what the tool is telling you.
Why the two sides exceed 100%
Add up the implied probabilities on both sides of a traditional sportsbook market and you will get more than 100% — perhaps 105% or 110%. That excess is the vig, the bookmaker’s built-in margin, and it means the raw implied probabilities are slightly inflated. On a prediction-market exchange the two sides sit much closer to 100%, because the platform charges an explicit fee instead of baking a margin into the price. To recover the market’s true estimate from vig-laden odds, you strip the margin out — see no-vig fair odds.
Putting it to work
The reason any of this matters is value. Once a price is a percentage, you can compare it directly with your own estimate of the same event: if you think something is 55% likely and the market implies 40%, the contract looks cheap; if the market implies 70%, it looks dear. That comparison — your probability against the market’s — is the foundation of finding value, and implied probability is simply the common language that makes it possible.
Frequently asked questions
How do you calculate implied probability from a contract price?
For an event contract that settles at $1 or $0, divide the price in cents by 100. A contract at 62¢ implies about a 62% chance. Your profit if it wins is the difference between the price and $1 — 38¢ on a 62¢ contract.
How do you convert betting odds to a percentage?
Decimal: 1 divided by the odds (2.50 → 40%). Fractional: the denominator over the sum of both numbers (3/2 → 40%). American positive: 100 ÷ (odds + 100), so +150 → 40%. American negative: the absolute odds ÷ (that value + 100), so −200 → 66.7%. An odds converter does all of these instantly.
Why do the two sides of a market add up to more than 100%?
Because traditional odds include the bookmaker’s margin, or vig, which inflates the implied probabilities. The excess above 100% is the overround. Prediction-market exchanges sit closer to 100% because they charge an explicit fee instead; removing the margin gives the no-vig fair odds.