How do you convert prediction market odds to probability?

Short answer

In a prediction market, the price of a contract in cents equals the probability of that outcome as a percentage. A contract trading at 60 cents implies a 60% probability of the event occurring.

What to know

Prediction markets work by letting participants buy and sell contracts that pay out one unit of currency if a specific outcome occurs and nothing if it does not. Because the maximum payout is one dollar, the price at any moment reflects what the collective market believes the chance of that outcome actually is. A price of 0.60 means participants are willing to pay 60 cents for a potential one-dollar payout, implying they believe the odds of it happening are roughly 60%.

This relationship is direct and linear. There is no formula to memorize beyond recognizing that price equals probability. If a contract costs 30 cents, the implied probability is 30%. If it costs 85 cents, the implied probability is 85%. The math is intentionally transparent so that anyone can read the market at a glance.

It is worth noting that market prices are not predictions by any single authority. They emerge from many buyers and sellers each acting on their own information and beliefs. When new information arrives, participants revise their estimates and the price shifts to reflect the updated consensus. This is what makes prediction markets useful as a forecasting tool rather than just a betting mechanism.

The complement rule also applies. If one outcome has an implied probability of 60%, the opposing outcome carries an implied probability of roughly 40%, since the two must sum to 100% in a binary market. In markets with more than two outcomes, all the contract prices should sum to approximately one dollar in total.

Key points

• A contract price in cents translates directly to a percentage probability with no additional conversion needed.
• A price of 0.01 implies roughly 1% probability; a price of 0.99 implies roughly 99% probability.
• Prices move continuously as participants respond to new information, so implied probabilities are always live estimates.
• In a binary market, the probability of one outcome plus the probability of the other outcome should sum to approximately 100%.
• The market price reflects collective judgment, not a guaranteed forecast, and can be wrong.
• Some platforms charge a small fee on trades, which can cause prices to differ very slightly from pure probability values.

Steps

1. Find the current trading price of the contract you are looking at, expressed as a decimal or in cents.
2. If the price is shown as a decimal such as 0.72, multiply by 100 to get the percentage: 72%.
3. If the price is already shown in cents, that number is directly the implied probability percentage.
4. To find the implied probability of the opposing outcome, subtract from 100. A 72% implied probability for one side means roughly 28% for the other.
5. In a market with more than two outcomes, read each contract's price separately and note that all prices in the same market should sum to close to one dollar.
6. Compare the implied probability to any independent estimate you have, such as a poll or a model, to see whether the market agrees or disagrees.
7. Remember that the price can change at any time, so re-check it rather than relying on a number you read earlier.

How it compares

• Traditional polls give a point-in-time snapshot based on a fixed sample, while prediction market prices update continuously as participants trade.
• Sports betting odds are expressed in formats like moneyline or fractional odds that require conversion steps; prediction market prices skip that step since price equals probability directly.
• Weather probability forecasts are produced by models and updated on a schedule, whereas prediction market probabilities shift in real time with every trade.
• Stock prices reflect expected future cash flows rather than a binary outcome, so they do not map to probability in the same direct way.

FAQ

What if the prices in a market add up to more than 100%?

A small amount of overround is common and usually reflects trading fees or the bid-ask spread built into the platform. The excess above 100% represents a margin that goes to the platform or to liquidity providers rather than a forecasting error.

Can a contract price ever be zero or one?

In practice, prices stay just above zero and just below one while a market is still open. A price at exactly zero or one effectively means the outcome is considered certain, which would stop meaningful trading. Most platforms close markets and settle contracts once the outcome is officially resolved.

Does a higher price always mean a more likely outcome?

Yes, by definition within the market itself. A higher price means participants are collectively willing to pay more for that contract, which implies they assign it a higher probability. Whether that collective judgment is accurate depends on the quality of information participants are using.

How does implied probability differ from true probability?

Implied probability is what the market price suggests. True probability, if it could be known, is the actual likelihood of the outcome. Markets aim to track true probability as closely as possible, but they are estimates made under uncertainty and can deviate from reality, especially in fast-moving situations or thin markets.

Why do prediction market probabilities sometimes differ from poll results?

Polls measure stated opinions of a sample group at a point in time. Prediction markets aggregate the financial commitments of participants who have real incentives to be accurate. The two methods capture different information and neither is always more accurate, but they often diverge when a poll sample does not reflect broader sentiment or when new events have occurred since the poll was conducted.

Is a 60% probability contract a good purchase?

That is a question of personal judgment, risk tolerance, and whether you believe the true probability is higher or lower than 60%. This page does not offer advice on whether any contract represents a good trade.