Arbs › Guides › Polymarket vs sportsbooks: fees, limits and settlement
Polymarket vs sportsbooks
Arbs research desk · Updated 2026-11-01 · Reviewed 2026-11-01 · 2 min read
The short answer: A sportsbook sets the price and builds in a margin. Polymarket is an exchange where traders set the price and takers pay a small fee. The same game can be priced differently on each, which is why it pays to compare.
Who sets the price
A book’s traders set a line and shade both sides so the implied probabilities add to more than 100%; the excess is the vig. On Polymarket the price is wherever buyers and sellers meet, and there is no built-in vig. You pay the bid–ask spread and, on taker orders, a fee.
A book’s margin on a market is the sum of the implied probabilities minus one:
M = (1 ÷ d₁ + 1 ÷ d₂ + …) − 1
Worked example: A −110 / −110 line
- −110 is 1.909 in decimal, an implied 52.38% per side
- 52.38% + 52.38% = 104.76%
The margin is 4.76%.
At a glance
| Sportsbook | Polymarket | |
|---|---|---|
| Price set by | The book’s traders | Buyers and sellers on the order book |
| Built-in cost | Margin in every line, about 4.5% at −110 | Bid–ask spread plus a taker fee |
| Fee on resting orders | Not applicable | None for makers |
| Limits for winners | Books can cut your maximum bet | No account limits; size is set by depth |
| Leaving early | Cash-out on some bets, at the book’s price | Sell your shares at the bid |
| Settlement | House rules | The rules written on each market |
What a coin flip costs on each
The cleanest comparison is the cost of $1 of payout on an outcome that is truly 50%. A fair price is 50¢; anything above it is what the venue keeps.
| How you bet | Cost | Above fair |
|---|---|---|
| Book at −110 | 52.38¢ | 2.38¢ |
| Book at −105 (reduced juice) | 51.22¢ | 1.22¢ |
| Polymarket taker, ask 51¢ | 52.25¢ | 2.25¢ |
| Polymarket taker, ask 50¢ | 51.25¢ | 1.25¢ |
| Polymarket maker, filled at 50¢ | 50.00¢ | 0 |
Crossing a one-cent spread as a taker costs about the same as a −110 line. Where Polymarket wins is a tight book, a resting order that gets filled, and lines far from 50¢, where the fee shrinks.
Limits and selling early
Books can cut the maximum bet of winning customers. An exchange does not limit you for winning; your size is limited by the liquidity on the order book.
On Polymarket you can sell shares before the game ends at the current bid. Books offer cash-out on some bets, at a price they choose and usually with extra margin.
Settlement
Books grade bets by their house rules: whether overtime counts, what happens when a player does not start, when a postponed game is void. Polymarket settles each market by the rules written on that market. Read both before you compare prices or try an arbitrage between them.
Using both
Arbs compares Polymarket with the books on every game and shows where each side is cheapest. Free accounts see the model probability next to the Polymarket price; Pro adds the best venue and the edge.
Try it: Arbitrage calculator
Frequently asked questions
Is Polymarket cheaper than a sportsbook?
Often, but not always. Crossing a one-cent spread as a taker costs about as much as a −110 line on a coin flip. Resting maker orders, tight books and prices far from 50¢ are where Polymarket is cheaper.
Does Polymarket limit winning bettors?
No account limits for winning. How much you can buy at a given price depends on the order book.
Can the same game have different odds on Polymarket and DraftKings?
Yes. They are separate markets with different customers, so prices drift apart, especially near news.