Kalshi vs Polymarket: the complete 2026 comparison

Kalshi vs Polymarket at a glance

Are Polymarket and Kalshi the same thing?

No. They are separate, competing companies. Both run prediction markets — exchanges where you buy contracts that pay $1 if an event happens and $0 if it does not, so the price reads as a probability. But they were built from opposite ends.

Kalshi (founded 2018 by Tarek Mansour and Luana Lopes Lara) went to the regulator first: the CFTC designated KalshiEX LLC as a contract market on 3 November 2020, and it has always settled in US dollars with full KYC.

Polymarket (founded 2020 by Shayne Coplan, legal entity Blockratize Inc.) started as a crypto-native exchange settling in USDC. After a 2022 CFTC settlement it blocked US users, then bought the CFTC-licensed exchange QCEX in 2025 and relaunched in the US as Polymarket US (QCX LLC), designated by the CFTC on 9 July 2025. Today 'Polymarket' means two venues: the regulated US exchange and the international crypto platform.

Which came first, Kalshi or Polymarket?

Kalshi came first as a company (2018) and as a regulated exchange (CFTC designation in November 2020). Polymarket launched its product in mid-2020, a few months before Kalshi went live, but operated outside US regulation until its 2025 acquisition of QCEX.

Which is bigger: Kalshi or Polymarket?

By trading volume, Kalshi is now clearly bigger. Bernstein estimates Kalshi's share of industry volume rose from roughly 35% in 2025 to about 60% through August 2026. One seven-venue tracker that counts every contract at $1 face value put September 2026 at $60.7B for Kalshi (78%) versus $8.8B for Polymarket US (11%) and $4.6B for Polymarket international (6%).

Most of Kalshi's lead comes from sports contracts. On global political and geopolitical questions, Polymarket's international book is still usually the deepest.

By valuation, both are in the same league: Kalshi raised $1B at a $22B valuation in 2026 and was reported in talks at about $40B in late September; Polymarket raised at $15B in April 2026 after a strategic investment from NYSE owner ICE (up to $2B, of which $1.6B confirmed invested). Figures in talks are not closed rounds.

Kalshi vs Polymarket fees

Fees are now almost identical, because both use a formula that peaks when a contract trades at 50¢ and falls towards zero near 1¢ or 99¢.

Kalshi: fee = round-up(0.07 × contracts × P × (1 − P)). Buying 100 contracts at 50¢ costs about $1.75 in fees. Resting (maker) orders generally avoid the taker fee.

Polymarket US: taker fee = 0.0695 × C × P × (1 − P), about $1.74 per 100 contracts at 50¢; makers receive a small rebate (0.0125 × C × P × (1 − P)), and high-volume takers get 10–50% rebates.

Polymarket international: taker fee = C × r × P × (1 − P) where r is 0.07 for crypto, 0.05 for sports/economics/culture, 0.04 for politics/finance/tech and 0 for geopolitics. Makers pay nothing. The old '0% fees on Polymarket' claim is no longer true for most categories.

Is Kalshi or Polymarket legal in the US?

Both are federally regulated by the CFTC, but state-level fights over sports contracts decide what you can trade where. Federal appeals courts are split: the Third Circuit sided with Kalshi in New Jersey (April 2026), while the Ninth (Nevada) and Sixth (Ohio, Tennessee) Circuits ruled against it. A Supreme Court petition is pending.

Polymarket US says trading is unavailable only in Nevada (state injunction, 29 May 2026). New York, Wisconsin, Kentucky and the city of Baltimore have sued; none had produced an operative statewide ban as of 12 October 2026.

Kalshi must geofence sports contracts in Nevada (sports, election and entertainment contracts) and Michigan (sports, from 1 September 2026). Non-sports markets such as Fed decisions and CPI remain available nationwide. Full state-by-state detail: Are prediction markets legal in the US?.

Kalshi vs Polymarket outside the US

Kalshi opened to participants in 140+ countries in October 2025 but its member agreement (1 October 2026) restricts event-contract trading in 55 jurisdictions, including the UK, Canada, India, Switzerland, Australia, Belgium, France, Italy, Poland, Portugal, Ireland, Hungary and Bulgaria. Germany and the Netherlands are not on Kalshi's list, but national regulators there consider these products unlicensed gambling.

Polymarket international blocks new trades from the US, UK, France, Germany, Belgium, the Netherlands, Poland, Australia, Ontario, Singapore, Thailand, Taiwan and others, and regulators have ordered website blocks in Switzerland, Italy, Spain, Portugal, India and Brazil.

Practical takeaway: in the UK and most of the EU, neither platform is a legal option. See UK, Germany, EU and best Polymarket alternatives.

Which is better: Kalshi or Polymarket?

• US resident trading sports or US macro (Fed, CPI, jobs): Kalshi — deepest liquidity and the widest US market list.
• US resident trading politics, culture or crypto: compare prices on both; Polymarket US often lists the same events and fees are equivalent.
• Outside the US, in a country where Polymarket is accessible: Polymarket international — the deepest global political and geopolitical books, zero fees on geopolitics.
• UK / EU / Switzerland / India / Australia: neither. Use licensed exchanges where they exist, or follow the odds for free on TomorrowAlpha.

Do Kalshi and Polymarket give the same odds?

On the same event they usually trade within a few percentage points, because arbitrage traders close larger gaps. Differences persist when contract wording differs (resolution source, deadline time zone) or when one book is thin. TomorrowAlpha shows both prices side by side on each live market — always read the resolution rules before comparing.