Sportsbook odds vs prediction market prices for the NFL

A Sunday in October, one browser tab open to a sportsbook and another to a prediction market, both showing the same NFL game. The sportsbook says the home team is -150. The prediction market says 58¢. They are two ways of writing a probability. Here is how to translate one into the other, what the vig is, and why the legal fight over sports contracts as of late September 2026 matters to anyone choosing where to play.

How does a moneyline convert to an implied probability?

A moneyline converts to an implied probability with one of two formulas. For a favorite (a negative number), divide the absolute value of the line by itself plus 100. For an underdog (a positive number), divide 100 by the line plus 100.

Take a game with the home team at -150 and the visitors at +130. The favorite works out to 150 / 250, or 60.0%. The underdog works out to 100 / 230, or 43.5%. Those two numbers do not add up to 100%.

What is the vig, and where does it show up?

The vig (short for vigorish, also called juice) is the cut a sportsbook takes for accepting a bet. Roy Larking explained in Sports Illustrated that at -110 you must risk $11 to win $10, and that -110 implies about a 52.4% chance of the outcome. The same piece describes the vig as how a book profits when it takes balanced action on both sides.

Run the arithmetic on a standard point spread priced at -110 on both sides. Each side implies 52.4%, so the two together total about 104.8%. That extra 4.8% is the margin built into the price.

In our -150 / +130 example the implied probabilities total 103.5%. To strip out the margin, divide each side by the total. The favorite becomes 60.0 / 103.5, or about 58.0%, and the underdog becomes about 42.0%. That is the sportsbook's own estimate once its fee is removed, and it is the number to compare with a prediction market.

How does an exchange-style market price the same game?

In an exchange-style market, a contract that pays 100¢ if the home team wins trades at a price between 1¢ and 99¢, and that price is read directly as a probability. A "yes" at 58¢ and a "no" at 42¢ add up to exactly 100¢, so there is no overround baked into the quote.

That does not mean the trade is free of cost. On an order book, the cost is the spread between the best bid and the best offer, plus any platform fee. In an automated market maker, it is slippage as your trade moves the price. A sportsbook sets the number and you take it or leave it, while a market lets you post your own price and wait. See how market odds and resolution work for more.

What is the legal fight over sports event contracts?

The fight is over who regulates a contract that asks whether a team will win. Platforms registered with the CFTC argue that these contracts are federally regulated swaps. States argue they are sports bets, which states license and tax under their own gambling laws.

As of late September 2026, the federal appeals courts have split. On 6 April 2026, the Third Circuit ruled 2-1 for Kalshi against New Jersey regulators, as Sarah Wynn reported for The Block, finding the Commodity Exchange Act gives the CFTC exclusive jurisdiction over trades on designated contract markets. On 28 August 2026, the Ninth Circuit went the other way in Nevada, holding that Kalshi had not shown it was likely that federal law preempts Nevada's gaming rules for its sports contracts. According to that report, a CFTC spokesperson said the ruling "now teed up a circuit split that calls out for resolution by the Supreme Court."

Then, on 25 September 2026, the Sixth Circuit ruled unanimously against Kalshi in cases from Ohio and Tennessee, as CNBC's Davis Giangiulio reported that day. The panel held that Kalshi had not shown its contracts are swaps and, alternatively, that the Act does not preempt those states' gambling laws. PYMNTS reported on 29 September 2026 that the opinion, written by Judge Julia Smith Gibbons, called the contracts "virtually indistinguishable from" sports bets.

Where does the CFTC stand?

The CFTC sides with the platforms. PYMNTS reported that the agency backed Kalshi in an amicus brief in the Sixth Circuit, arguing the contracts fall within its exclusive jurisdiction. CNBC reported that the CFTC has also sued nine states to defend what it considers its exclusive authority over event contracts.

Kalshi's response to the Sixth Circuit loss, given to CNBC by spokesperson Dani Lever, was that the ruling "shows exactly why a state-by-state patchwork doesn't work." CNBC also reported that New Jersey has petitioned the Supreme Court after its April loss. Our post on what the circuit split means covers how this reaches the justices. Nobody can say yet how it ends.

What does the NFL think about all this?

On 4 September 2026, ABC News's Luke Barr reported that the NFL sent a letter from chief compliance officer Sabrina Perel asking Polymarket and Kalshi to stop listing "objectionable" bets. The letter named contracts on player injuries and misconduct, broadcast mentions, officiating counts such as flags thrown, and single-play outcomes like a kicker missing a field goal. It was the second such letter that year.

Commissioner Roger Goodell had said earlier, as Daniel Roberts reported for Front Office Sports on 9 December 2025, that joining prediction markets is "not something we're about to enter into" without a regulatory framework and more comfort on integrity.

Where does a free-to-play market fit?

Some people like the forecasting: reading a line, deciding it is a few points off, and checking later. They may not want the part where money changes hands, and the legal uncertainty above is one more reason.

Ravioli is a free-to-play version of that game. Trades use Sense, which is free play credit (new accounts start with 1,000), so there is no deposit, no KYC and no money at risk. There is both an automated market maker for instant trades and a limit order book, and sports markets include live scores, so you can watch a price move as a game does. The prizes are real, but nothing you trade is cash.

The limits are plain. A play-money market is a place to practice calibration, not proof you would profit with real stakes, and its prices are not claimed to beat a sportsbook's. One NFL Sunday is a small sample. To start, see how to make your first prediction and prediction markets vs. sports betting.

Ravioli is a free-to-play prediction market. You trade with Sense, which is free, and the prizes are real.

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