How prediction markets work for sports betting

On a prediction market such as Kalshi or Polymarket US, a sports bet is a contract that pays $1.00 if a stated outcome happens and nothing if it doesn't. Its price in cents is the probability the market puts on it — a 60¢ Yes means 60% — and converting it to sportsbook odds is one division: 60¢ is decimal 1 ÷ 0.60 = 1.667, or −150. You buy from other traders through an order book, pay a trading fee when the order fills, and can sell before the game ends. The rest of this guide is what each of those pieces means for the price you actually get.

Yes, No, and what a contract is

Each market is a yes-or-no question: “Will Team A win this game?” Buying Yes at 60¢ pays $1 if A wins. Buying No pays $1 if A doesn't. Because one of the two always pays, a Yes and a No together are always worth exactly $1, so the No price is roughly 100 minus the Yes price. The contract's rules — which the venue publishes with every market — say exactly what counts: a Kalshi soccer market, for example, is settled after 90 minutes plus stoppage time, without extra time or penalties, and has a separate Tie market.

The order book: bid, ask and depth

Nobody sets the price. Traders leave orders on the book: bids to buy at a price, and asks (offers) to sell. The best ask is what you pay if you buy now; the best bid is what you get if you sell now. Buying Yes is the same trade as selling No, so a Yes bid of 58¢ shows up as a No ask of 42¢. Each price level holds a limited number of contracts, and if you want more than the best level holds, the rest of your order fills at worse prices. On a sportsbook the quoted odds are good for whatever the book will let you stake; here the quoted price is only good for the size resting at it.

Settlement, and selling early

When the game is final, each winning contract pays $1.00 into your account and losing contracts pay nothing; Kalshi's fee schedule lists no settlement fee. Before that you can sell your contracts back into the book at the current bid, which is how people take a profit or cut a loss mid-game, paying the trading fee again on the sale. Read the contract's rules for the edge cases, because they are not a sportsbook's: in the Kalshi NHL and tennis markets we read, a game cancelled or not started within the stated window resolves “to a fair price” set under the rules, rather than being refunded like a voided sportsbook bet.

Comparing a contract with sportsbook odds

Convert the ask to decimal, then take the fee into account before you compare. A 60¢ Yes is −150 on paper and about −161 after Kalshi's standard taker fee, so it only beats a sportsbook's −155 if you can buy it cheaper, rest an order instead of taking, or the market carries a lower fee multiplier. The sportsbook price also has a hidden cost the contract doesn't: winning there eventually gets your stakes capped, while an exchange has no house position to protect. Implied probability and fair odds are the tools for the comparison.

The legal status, as of September 27, 2026

Kalshi, Polymarket US, Novig and ProphetX operate as CFTC-regulated designated contract markets and offer sports contracts across most of the country, but whether states can apply their gambling laws to those contracts is unresolved. On April 6, 2026 the Third Circuit (KalshiEX v. Flaherty) upheld an injunction stopping New Jersey from enforcing its gaming law against Kalshi, finding Kalshi likely to win on federal preemption. On August 28, 2026 the Ninth Circuit (KalshiEX v. Assad) went the other way for Nevada, affirming the dissolution of Kalshi's injunction and concluding that sports event contracts are likely not “swaps” and that Nevada's gaming rules are likely not preempted. New Jersey asked the Supreme Court to take the question on September 2, 2026. Availability can change state by state as these cases move; this is general information, not legal advice, and the venue's own eligibility page is the one to trust on the day.

Where TrueEdge fits

The Order Book board lists plays where both legs are exchange or prediction-market prices, with the return shown after the venues' trading fees and, once you enter a stake, the fee in dollars under the card. Each exchange leg also shows the size resting at its price and how a larger stake would fill down the book, so you can see where the quoted price runs out. The Order Book walkthrough works one play through from the card to the fill.