How Prediction Market Prices Become Probabilities
Prediction-market prices become probabilities because every contract has a fixed $1 payout. If a Yes contract pays $1 and trades at 25¢, the rough implied probability is simply 25%.
The formula is the price
Price in cents ≈ implied probability. So 8¢ means about an 8% chance, 62¢ means about 62%, and 91¢ means about 91%. Interactive Brokers makes the same point about event contracts: they generally trade between about $0.01 and $0.99 depending on the market’s perceived likelihood.
A contract on “Will inflation top 3% this month?” trades at 40¢. The crowd is pricing roughly a 40% chance. If new data pushes the odds up, buyers move in and the price drifts toward 55¢ or 60¢ — the probability re-rating in real time.
Why it is only approximate
The cents-equals-percent rule is a close estimate, not gospel. Bid-ask spreads, fees, and traders’ appetite for risk all nudge the price. A contract at 50¢ does not mean the event is objectively 50/50 — it means buyers and sellers currently agree to trade around that level.
How to use it
Read the price as the market’s best guess, then form your own. If you think the true probability is higher than the price implies, the Yes side may be cheap; if lower, the No side may be. That gap is the whole game — see can you make money on prediction markets? for how traders try to exploit it.