Prediction markets vs sports betting: the real differences

The short version, for a US reader comparing a sports contract on an exchange with a bet at a sportsbook. Each row is explained further down.

This is the structural difference and everything else follows from it. A sportsbook takes the opposite side of your position itself. It profits when its customers collectively lose, manages its exposure by moving prices, and can decline, limit or close your action if the arrangement stops working in its favour.

A prediction market matches you against another participant. Somebody had to be willing to sell you the contract at the price you paid, which means the price is the point where two opposing views met rather than a figure a firm decided to offer. The venue takes a fee for running the matching and holds no position in the outcome.

That distinction is why an exchange has no reason to restrict a consistently profitable participant, and why a book often does. It is also why an exchange can show you a price nobody is prepared to trade at — the wide-spread problem — while a book always has a price, because it is the one making it.

Both venues charge for the service, and in both cases the charge is visible in the fact that the two sides of a market add to more than certainty. A book quoting decimal odds of 1.80 and 2.10 on the two sides is implying 1 ÷ 1.80 = 55.6% and 1 ÷ 2.10 = 47.6%. Those sum to 103.2%, and the 3.2 points of excess is the book’s margin.

The arithmetic to recover the probabilities is the same one an exchange requires: divide each by the sum. 55.6 ÷ 103.2 = 53.8% and 47.6 ÷ 103.2 = 46.2%, which now add to 100%. An exchange market quoting YES 64¢ and NO 40¢ needs 64 ÷ 104 = 61.5% by exactly the same logic. The formula does not care which kind of venue produced the numbers.

What differs is who receives the excess and what determines its size. A book sets its margin as a commercial decision and keeps it. On an exchange the spread is captured by whichever participant was standing at the front of the queue, and its width is set by competition between them — so it can be far narrower on a heavily traded market, and far wider on a neglected one. Neither arrangement is automatically cheaper. A liquid exchange market is usually cheaper than a book on the same event; an illiquid one frequently is not.

Illustrative prices, not live quotes. A sportsbook offers Team A at −150 and Team B at +130. An exchange has Team A’s YES contract offered at 58¢ and Team B’s at 43¢.

• Sportsbook: −150 implies 150 ÷ 250 = 60.0% and +130 implies 100 ÷ 230 = 43.5%. Together that is 103.5%, so 3.5 points are the book’s margin. Stripped out, Team A is about 58.0%.
• Exchange: 58¢ and 43¢ add to 101¢ — a 1¢ spread. Kalshi’s general trading fee is 0.07 × contracts × price × (1 − price), rounded up to the cent: on 100 contracts at 58¢ that is $1.71, so 100 contracts cost $59.71 and pay $100 if Team A wins.
• Same stake, same outcome: $59.71 on Team A wins $40.29 on the exchange and $39.81 at −150. To break even you need Team A to win 59.7% of the time on the exchange and 60.0% at the book.

The exchange is slightly cheaper here, and only slightly: one cent of extra spread, or a sportsbook price boost, reverses it. Some venues charge nothing on certain trades — Novig, for example, charges no fee on pre-game straight trades — which widens the gap. The habit worth keeping is to compare the all-in price, fee included, on the size you actually trade. The expected value calculator and fees and the true cost of a trade do that arithmetic for you.

Starting from a point spread rather than a price? The point spread calculator turns an NFL or college football spread into the win probability it implies and the contract price that matches it.

A book’s price is not purely a forecast. It is a forecast adjusted for the book’s exposure and for what its customers are doing: if money piles onto one side, the price moves to attract the other side, whether or not any new information arrived. Reading it as a clean probability estimate means reading a number that has commercial risk management mixed into it.

An exchange price is closer to a forecast because there is no book to balance, but it is not pure either. It reflects who happens to be trading, how much capital they have committed, and what it costs them to hold the position until settlement. On a thin market it can be one participant’s opinion. It is a better probability estimate than a book’s price on average, not by construction.

The honest summary is that the exchange price is a measurable estimate with a measurable distortion, and the book’s price is an estimate with a distortion you cannot see the size of. That is a real advantage, and it is a smaller one than the framing usually suggests.

A prediction market position trades until it settles, so you can sell it at whatever it is worth at any point. A view that turns out to be right early can be realised early; a view that turns out wrong can be closed at a partial loss rather than run to zero. The price you get is set by the book, not by the venue’s goodwill.

A fixed-odds bet is generally held to the event. Where a cash-out is offered it is offered at the book’s price, which includes the book’s margin a second time — so a settled-looking position often cashes out for meaningfully less than its true worth.

You can also be the one quoting. Posting a limit order on an exchange means other participants trade against your price, and if it is filled you have captured part of the spread rather than paid it. There is no equivalent at a sportsbook, where the price is the house’s to make.

Sportsbooks are licensed by each state’s gaming regulator, so whether you can bet at all — and from what age — depends on the state you are in when you place the bet. US prediction markets are exchanges designated by the Commodity Futures Trading Commission; what the CFTC is and what designation means explain that status.

Age is set by the venue rather than by a single federal rule. Novig requires users to be 21 or older; Polymarket US requires participants to be at least 18 and of the age of majority in their state; ProphetX requires the higher of 18 and the local age of majority. Location works as it does at a sportsbook: eligibility follows where you are when you trade, not where you live.

Federally, no — and that is the whole dispute. The CFTC describes event contracts as typically structured as swaps, regulated as derivatives, and says that under federal law prediction markets can operate in all 50 states (cftc.gov). On 2 April 2026 it sued Arizona, Connecticut and Illinois over their actions against designated exchanges (release 9206-26).

Several states treat sports contracts as wagering under their own law, and some have won orders against Kalshi: in Nevada a district court injunction bars its sports, election and entertainment contracts; in Washington a King County order covers sports and several other categories; in Michigan an injunction of 1 September 2026 covers sports contracts. The courts have not settled the question nationally. The full picture is in are prediction markets legal in the US? and the product itself in what event contracts are.

Sports betting winnings are gambling income: the IRS says “gambling winnings are fully taxable” and names sports betting among them (IRS Topic 419). How gains on event contracts are taxed is not settled, and it is not obviously the same — see event-contract taxes in the US. Ask a tax professional before you assume either way.

Both sides run welcome offers, but they work differently. Sportsbooks typically pay bonus bets or deposit matches. Prediction markets usually give trading credits: you can trade with them and keep the settled winnings, but the credit itself cannot be withdrawn, and most expire. Each operator’s own terms, with what they are worth in practice, are on our bonuses page.

The risk of loss is identical in kind. You can lose everything you committed on either, and being correct about the world is not sufficient — paying too much for a correct view still loses money. Neither instrument is a savings product and neither becomes safe by being regulated.

The legal treatment, on the other hand, is not the same and is not stable. Event contracts are regulated as financial instruments in some jurisdictions and as wagering in others, and the classification is being actively argued about in several. Nothing here is legal advice; check your own position before assuming which set of rules applies to you.

• A prediction market suits you if you want to sell before the final whistle, set your own price with a limit order, see the fee separately, or trade often enough that a book might limit you.
• A sportsbook suits you if you want parlays and props in depth, bonus bets, or a guaranteed price on a market an exchange trades thinly.
• Either way, compare the all-in price on the same game before you commit, and check that the venue is open in your state.

Our ranking of the best prediction markets for sports lists every venue with sports contracts, with fees and availability for your region. The US venues most often compared with a sportsbook are Kalshi, Novig, ProphetX, FanDuel Predicts and DraftKings Predictions — side by side in Kalshi vs FanDuel Predicts, Kalshi vs Novig and FanDuel Predicts vs DraftKings Predictions.