How does Polymarket pricing work?

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Accepted Answer

Polymarket is a prediction market, so its pricing works differently from a typical exchange. Here's how it works.

The core idea: price = probability

Every market is a binary bet on whether an event happens or not (e.g. "Will Trump win PA?" — YES or NO). The market price is expressed in USDC cents from $0.00 to $1.00, and that price is the market's implied probability.

If a share trades at $0.65, the market thinks there's a 65% chance the event happens.
Shares settle at $1.00 if YES resolves true, or $0.00 if it resolves false.

This is why prediction-market prices read like percentages — you're literally buying a probability.

The two sides always sum to $1

The interesting mechanic: the YES share and the NO share are complements. If YES trades at $0.65, then NO trades at $0.35. A trader can always buy one of each and be guaranteed to get $1.00 back at settlement regardless of the outcome — that's what locks the two prices to sum to $1 (modulo tiny spreads).

How the price actually moves

Order book + AMM hybrid. Polymarket's core markets use an automated market-maker (an AMM similar to a constant-function market) alongside limit orders, so there's continuous liquidity rather than only matching buyers and sellers.
Arbitrage is the price-correcting force. If a market misprices a probability relative to the "true" odds, traders can buy the cheap side and either hedge on another market or capture the gap to fair value — this pushes the price back toward the actual probability.
Liquidity incentives. Polymarket pays rewards to liquidity providers who quote on both sides, which keeps spreads tight and prices efficient — the tighter the book, the more accurate the implied probability.

What makes it "efficient"

Prediction markets are considered good probability aggregators because the price reflects real money at risk. If the market price diverges from reality, someone stands to profit by betting against it, so the price tends to converge on the true likelihood — the same logic as why futures markets track spot prices.

One thing to note: the price is only as good as the market's liquidity and the accuracy of the event's resolution conditions. Thin markets and ambiguous resolution rules can distort the implied probability.

If you want, I can pull the current price on a live Polymarket-style outcome or check what's trending in crypto today — or look up a related token/tool if there's a specific angle you're exploring.