Polymarket vs Kalshi: fees, rules, access, and the odds

Kalshi is a CFTC-regulated exchange that takes dollars from US customers; Polymarket's global site is a crypto exchange on Polygon that takes USDC from everyone except US persons, with a separate US-regulated Polymarket app added in 2025. Both trade yes/no contracts that pay 100, and the same question often shows different prices on each, for reasons that are usually not mispricing.

The table is as of September 2026 and every row in it changes. Check the venue's own page before relying on it.

The comparison

	Kalshi	Polymarket (global)	Polymarket (US app)
Regulation	CFTC designated contract market	No US license; a 2022 CFTC settlement bars US persons	CFTC-licensed exchange acquired in 2025
Who can trade	US customers with verified identity, subject to the state disputes	Non-US persons; geoblocked in the US	US customers with verified identity
Currency	US dollars	USDC on Polygon	US dollars
Fees	Taker fee of 0.07 × price × (1 - price) per contract; maker fee lower or zero	No fee on most markets; a taker fee on some series	Its own schedule
Deposits	Bank transfer, debit card, wire	USDC transfer, bridge, or card via a third-party on-ramp	Bank rails
Market range	Economics, politics, weather, sports, culture; every contract CFTC-listed	Anything the venue lists, including questions US regulators would not permit	A narrower list under the CFTC framework
Settlement source	Rule text names the source; the exchange declares	Rule text plus the UMA optimistic oracle, with disputes settled by token vote	Rule text; the exchange declares
Volume units	Contracts, or dollars of notional	USDC traded (price × shares, summed)	Dollars

How Kalshi works and How Polymarket works go through each column; Kalshi fees explained has the fee schedule; Are prediction markets legal in your state covers the "who can trade" row, which is the one in court.

The volume row deserves a second look

Volume is the number most often compared across venues and least often comparable. Polymarket reports USDC traded, so 1,000 YES shares changing hands at 30% is $300 of volume. Kalshi reports contracts traded, and in places dollar notional, so the same trade is 1,000 contracts or $1,000. A headline saying one venue did three times the other's volume on a race may be comparing shares to dollars. Our most-traded markets page labels the unit for that reason.

Why the same question prices differently

Two venues, one headline, prices 3 points apart. Before calling it an arbitrage, run through the reasons it might be correct.

Different traders. Kalshi's book is US retail and institutions in dollars; the global site's book is international and crypto-native. Their information and their biases differ, and on political questions in particular the two crowds have disagreed by several points for weeks at a time.

Different capital costs. Money on the global site is USDC that had to be bought and will have to be sold, with an exchange fee on each end. Money on Kalshi is a bank transfer. A trader weighing whether to push a price 2 points does the sum differently on each.

Different fees. A Kalshi taker pays up to 1.75 cents a contract near 50%; a Polymarket trader on most markets pays nothing. That alone can hold a 1-point gap open, because closing it costs more on one side than the other.

Different liquidity. The venue with the deeper book has the more reliable price. The shallower one's displayed midpoint may sit on a spread wide enough to swallow the whole difference.

Different contracts. This is the big one, and it gets its own section.

The contracts are often not the same contract

"Will the Fed cut in October?" on one venue settles on the FOMC statement and counts any reduction in the target range. A contract with the same title on the other might settle on the effective federal funds rate, count only a 25-basis-point move, or resolve on a different date. A Senate control market on one venue can count independents who caucus with Democrats as Democrats while the other counts only registered party members. A Super Bowl market is usually the same on both, but the rule for a cancelled season is not.

When the two contracts differ, a price gap is not a mispricing; it is the market's estimate of the difference between two questions. How settlement works covers how to read two rule pages side by side, and it is the step people skip before betting that a gap will close.

A worked example

Say the Fed decision market shows a cut at YES 34% on Kalshi and YES 37% on Polymarket's global site. A trader tries to capture the gap by buying YES on Kalshi and NO on Polymarket.

Leg	Price	100 contracts	Fee
Buy 100 YES on Kalshi at the 34 ask	34%	$34.00	0.07 × 100 × 0.34 × 0.66 = $1.57
Buy 100 NO on Polymarket at the 63 ask	63%	$63.00	$0.00
Total outlay		$97.00	$1.57
Payout if the two contracts settle the same way		$100.00
Profit		$1.43

That is a 1.4% return on $98.57 committed until the meeting, and it assumes both fills at the quoted asks, not at the midpoints the cards show. Then the settlement risk: if the Fed cuts by 50 basis points and one contract's rule counts it while the other's is written around 25, the trader can hold a loser on both venues at once, and the $98.57 outlay becomes a $98.57 loss instead of a $1.43 gain. The gap was 3 points. The cost of being wrong about the rule was 100.

Which to use

That depends on where you live and what you want to trade, which is why this is a comparison and not a recommendation. A US reader's choice is between Kalshi and the Polymarket US app, and their market lists overlap on the big questions, the Fed, the Senate, the Super Bowl, and diverge on the rest. A reader outside the US has the global site. Sports contracts versus sportsbook bets covers the category the state cases are about.

What to check before you trade

• The rule page on both venues, read side by side, before assuming a gap is a mispricing.
• The bid and ask on each, not the displayed price.
• The fee on the leg that carries one.
• The unit behind any volume comparison.
• Whether you are permitted on the venue at all, and which Polymarket you are on.

Nothing on this page is investment advice, and the venue's current rule text and fee page are the only things that pay.