Polymarket vs. sportsbooks
Updated · 7 min read
A sportsbook builds its margin (the vig) into the odds and takes the other side of your bet. Polymarket is an exchange: you trade against other users, and your costs are a taker fee plus the spread. On busy markets that can be cheaper than a sportsbook's margin, and on thin markets it can be more expensive. Compare the real price on both before you bet.
How a sportsbook makes money
A sportsbook sets the odds and is the counterparty to your bet. The odds are shaded so that, across all the bets on a game, the book keeps a margin. In a classic two-way line priced at −110 on both sides, each side implies a 52.38% chance, so the two add up to 104.76%. The extra 4.76 points are the book's margin, about 4.5% of what is bet.
Parlays compound it. A three-leg parlay of −110 legs commonly pays +596 (about 6.96x total return), while the fair price for three 50/50 legs is 8x. That gap is a margin of roughly 13% on that bet.
How Polymarket is different
Polymarket does not take the other side of your trade; your counterparty is another user. It does not set the odds, either: prices come from supply and demand. Polymarket earns money from fees charged to takers on most markets, and you also cross the bid-ask spread. Details in Polymarket fees explained.
A worked comparison
Take a game that both places see as an even 50/50, and ignore the spread:
- Sportsbook at −110: a $1 stake returns about 1.91 in total (decimal odds 1.909).
- Polymarket at 50¢: 100 shares cost $50, plus a sports taker fee of $1.25, so about $51.25 buys $100. A $1 stake returns about 1.95 in total (1 ÷ 0.5125).
So in this idealised case Polymarket pays about 2% more per bet. Reality is messier: Polymarket's spread can be a few cents on quiet markets, which would erase the gap, and sportsbook prices differ from book to book. The lesson is to compare the actual prices on the game you want.
Side by side
| Polymarket | Typical sportsbook | |
|---|---|---|
| Who is on the other side | Another user | The sportsbook |
| Where the cost is | Taker fee + spread | Margin built into the odds |
| How odds are set | Supply and demand | The sportsbook |
| Selling before the event | Yes, at the market price | Cash-out, if the book offers it |
| Markets | Sports, politics, crypto, culture… | Mostly sports |
| Parlays | Combos on sports markets | Parlays, often with same-game options |
| Deposits | Crypto transfer described in the help center | Cards, bank transfer, e-wallets |
| Availability | Blocked in a published list of countries | Licensed market by market |
When Polymarket tends to be cheaper, and when not
- Liquid, high-profile games: tight spreads and a fee that is small for likely outcomes can beat a sportsbook's built-in margin.
- Long shots: the taker fee is a larger share of a cheap share's price (4.0% at 20¢ in the sports example), so the gap narrows or flips.
- Thin markets: a wide spread can cost more than any sportsbook margin.
- Parlays: a sportsbook's margin compounds on each leg. Combos on Polymarket are priced by competing market makers, so look at the quote you are given rather than assuming.
What else to weigh
- Access. Polymarket is not available everywhere. Its help center lists the countries that are blocked (and says VPNs must not be used to get around it), so check Polymarket's geographic restrictions and your local rules before you sign up.
- Funding. Polymarket's help center describes depositing by crypto transfer; sportsbooks accept cards and banks.
- Rules and settlement. Each Polymarket market resolves by its own written rules through UMA's Optimistic Oracle, while a sportsbook grades bets under its own terms. Read both.
- Risk. Either way you can lose your whole stake. Never bet money you need.
Frequently asked questions
Is Polymarket cheaper than a sportsbook?
It can be on liquid markets, because you pay a taker fee and the spread instead of a built-in margin. On thin markets or long shots it can be more expensive. Compare the actual prices.
What is the vig at a sportsbook?
The margin built into the odds. A standard two-way line at −110 on both sides carries about 4.5%.
Does Polymarket bet against me?
No. Polymarket does not take the opposite side of your trade; your counterparty is another user.
Can I cash out early on Polymarket?
Yes. You can sell your shares at the current market price at any time before the market resolves, if there is a buyer.
Are parlays cheaper on Polymarket?
Not necessarily. Sportsbook margins compound on every leg, but Combo prices depend on market-maker quotes, so compare the payout you are shown.