Every price you see on Predictions on the Betr app tells you something specific: the market's current read on how likely an outcome is. Here's how that number actually gets set.
Setting the very first price
A brand-new market doesn't launch with a starting price. There are no open positions yet. Instead, traders (often called market makers when they're the ones providing quotes) place orders at whatever level they're comfortable with.
Each market on Polymarket US has a single contract for the outcome. Buying the contract takes the YES side. Taking the NO side is recorded by the exchange as a short position in the same contract. A trade happens when a buy order and a sell order match at the same price.
For example, say a market asks whether Team A will win its game against Team B. If one trader bids 60¢ to buy YES and another trader sells at 60¢, which puts them on the NO side for a cost of 40¢ per contract, those orders match at 60¢, and that becomes the market's first traded price.*
How the price updates from there
Once trading is underway, the price you see reflects the midpoint between the best available bid and ask in the order book. If that gap between bid and ask ever widens past 10 cents, the display switches to the last price a trade actually happened at instead. In short, prices move the same way they do in any market: driven by whoever's buying and selling in real time. The displayed price is not necessarily the price at which your order will fill.
Reading price as probability
Picture a market where the bid sits at 34¢ and the ask sits at 40¢. The midpoint, 37%, is what gets shown as the market-implied probability. Once the spread crosses that 10-cent threshold, the probability shown switches over to the most recent trade price instead.
*The example above is for illustrative purposes only and does not reflect an actual market or outcome.
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Predictions on Betr are event contracts listed on Polymarket US (QCX LLC), a CFTC-designated contract market, and cleared through Polymarket Clearing (QC Clearing LLC). Betr provides the app you use to access Polymarket US. Betr is not the exchange or a broker. Trading event contracts involves risk, and you can lose the full amount you pay for a contract, plus fees. Each contract is governed by its contract terms and the Polymarket US Rulebook (https://polymarketexchange.com/files/legal/latest/rulebook).