Prediction basics
Prediction market odds: calculate your real return
Learn what a YES price means, how return differs from profit, and why the average fill, fees and final outcome matter more than a headline percentage.
A price is a market signal, not a guarantee
In a binary share market that pays 1 unit for a winning share, a YES price of 0.60 is commonly read as an implied 60% chance. It is the price attached to the claim, not a promise that the event will happen or a measured probability supplied by an independent referee.
How the displayed number is produced matters. Polymarket, for example, documents a midpoint between bids and asks, with a last-trade fallback for a wide spread. Inari’s practice markets can use an automated pricing curve. A percentage on screen does not, on its own, tell you how many people agree with it or what your whole order will cost.
Polymarket: how displayed prices are calculated ↗Return includes your stake. Profit does not.
Take a simplified example with no price movement or fees. You spend 24 units on YES at 0.60 per share. That buys 40 shares. If YES is the final result and each winning share pays 1 unit, your return is 40 units. Your profit is 40 − 24 = 16 units. The return multiple is 40 ÷ 24, about 1.67×.
If NO wins, those YES shares pay zero and the loss is the 24 units spent. This is why “40 back” and “40 profit” are very different claims. For a settled bet, use the recorded payment rather than an estimated position value.
This example describes an ordinary binary winning-share payout. A cancelled, disputed or otherwise exceptional market follows its own published rules; do not assume that every status pays either zero or one immediately.
Polymarket: winning-share settlement and market rules ↗Your first share and your last share can cost different amounts
An order can move along an automated pricing curve or consume several offers in an order book. The headline price may therefore differ from the average price you actually pay. The average fill is the relevant number for calculating how many shares your budget buys.
Suppose your total cost is 25 units, including an illustrative 0.10-unit fee. The remaining 24.90 buys shares at an average price of 0.60, giving 41.50 shares. A winning return of 41.50 means 16.50 profit after that entry fee, not 16.60. The fee and fill here are invented for the example; they are not a published fee schedule.
A larger order may get a worse average fill than a smaller one. On Inari, read the quote for your chosen side and amount. If it changes before confirmation, review the new figures rather than applying the card’s approximate return to your original budget.
Check costs before treating a price difference as an edge
Even if your probability estimate is good, the price can make a trade unattractive. If you estimate a 60% chance, a share costing 0.60 has an expected payout of 0.60 units before costs. Paying an additional fee makes the expected net result negative under that estimate. Paying 0.70 does not become good value simply because YES is more likely than NO.
That estimate can also be wrong. Fees, the difference between buying and selling prices, and price movement affect the result independently of whether you understood the event. Check the actual ticket, not a fee formula copied from another platform or an old screenshot.
A green position is not a completed payout
A position can rise in estimated value before the event ends. Realizing that value requires an available exit at a price you can actually receive, potentially with another fee. An order waiting for a counterparty is not a completed sale, and an indicative value is not money already paid to you.
If you hold to settlement, the result and its review process decide the payout. Closing time stops new betting; it does not necessarily make the outcome final. My Bets is where to distinguish an open position, an offer and a recorded settled amount.
Read five things on the ticket
Check the side, total amount you will spend, return if correct, loss if wrong, and decision rules. Include the currency: Inari’s public practice balance is play-money $INARI, not a withdrawable cash balance. A 1.67× practice return is not a promise of a 1.67× crypto payout.
Then decide whether the evidence and price fit your own view. Understanding the ticket gives you a cleaner decision; it cannot remove the uncertainty of the event.