Implied Probability Calculator
Convert any odds format to implied probability, or strip the vig from a two-outcome or multi-outcome market to find the fair probability on each side.
Enter a value in any field — all others update automatically.
0–100 cents
±100 or greater
Must be greater than 1.0
Format: numerator/denominator
What Is Implied Probability?
Implied probability is what a market price tells you about the likelihood of an event. When a prediction market contract trades at 65¢, the market is saying there is approximately a 65% chance that contract resolves YES. That probability is “implied” by the price — not independently calculated.
The same concept exists across all odds formats. A +200 American line, a 3.00 decimal odds line, and a 2/1 fractional line all imply the same 33.3% probability. This calculator converts between all four formats instantly so you can compare prices across sportsbooks and prediction markets that use different conventions.
For a full walkthrough of how prediction market pricing works, see the Prediction Market Translator.
How to Read Multi-Outcome Markets
Most prediction markets list contracts in binary YES/NO pairs, but some events have multiple possible outcomes — an election with three candidates, a race with five competitors, or a range market with several price buckets.
In a multi-outcome market, the raw implied probabilities (contract prices) typically sum to more than 100% because each outcome carries the market's overround. To compare outcomes fairly, you need to normalize the raw probabilities — this is what the Multi-Outcome Devig tab does.
Enter each outcome's price and the calculator strips the overround using multiplicative normalization, producing fair probabilities that sum to exactly 100%.
How Devigging Works
Markets don't set prices at pure probability — they include a margin. On a binary market, YES at 62¢ and NO at 43¢ sum to 105¢, which implies an overround of 5%. That 5% is the market's edge, built in regardless of which side wins.
Devigging divides each raw implied probability by the total to produce fair probabilities that sum to 100%:
YES fair: 62 / 105 = 59.0%
NO fair: 43 / 105 = 41.0%
Understanding the fair probability is important before using tools like the EV Calculator, which compares your own probability estimate against the market price. To see the overround in more detail, use the Vig Calculator.
Related tools
- Vig Calculator — see overround and devigged fair odds
- Prediction Market Translator — price to payout in plain English
- EV Calculator — factor in fees and your own probability estimate
- What Is an Event Contract? — how prediction market contracts work
- Prediction Market Arbitrage — fair probability math is the foundation of cross-platform arb
Frequently Asked Questions
What is implied probability?
Implied probability is the probability of an event occurring as priced by the market. A contract trading at 65¢ implies a 65% probability of resolving YES. It's called 'implied' because it is derived from the price, not calculated independently.
How do you convert American odds to implied probability?
For negative American odds (e.g. -150): divide the absolute value by the absolute value plus 100. -150 → 150 / 250 = 60%. For positive odds (e.g. +200): divide 100 by the odds plus 100. +200 → 100 / 300 = 33.3%.
What does 'devigging' mean?
Devigging removes the bookmaker or market's built-in margin (the vig or overround) to find the fair implied probability. On a two-outcome market, YES and NO prices sum to more than 100¢ — the excess is the vig. Devigging normalizes the raw implied probabilities so they sum to exactly 100%.
What is overround in prediction markets?
Overround (also called the vig or juice) is the percentage by which the implied probabilities on all sides of a market exceed 100%. It represents the market's built-in edge. A YES price of 62¢ and NO price of 43¢ sum to 105¢ — the overround is 5%. This is what the market maker earns regardless of outcome.
Educational content only. Implied probability calculations are based on market prices and do not represent independent probability estimates. Prediction market trading carries risk. Not financial advice.