Both let you buy a contract on a yes-or-no question, priced between 1¢ and 99¢, that pays $1 if you're right and nothing if you're wrong. A price of 70¢ means the market, roughly, thinks there's a 70% chance. Past that, the two are built quite differently.
The short version
| Kalshi | Polymarket | |
|---|---|---|
| What it is | A US exchange regulated by the CFTC as a designated contract market | Two platforms: polymarket.com, an international exchange that runs on a blockchain, and Polymarket US, a separate US-regulated exchange |
| Who can use it | US residents, after ID verification; some contracts are unavailable in some states | polymarket.com is for users outside the US; Americans use Polymarket US |
| Money | US dollars from a bank account or card; crypto deposits are also accepted | polymarket.com: a dollar stablecoin (USDC) in a crypto wallet |
| Fees | A trading fee that depends on the price, highest near 50¢; some markets also charge makers | polymarket.com: takers pay a fee by category, makers pay nothing; geopolitics markets are fee-free |
| Who decides the outcome | Kalshi, under each market's written rules | polymarket.com: an outside oracle (UMA), where a proposed result can be challenged |
Regulation and who can trade
Kalshi is a federally regulated exchange in the US, overseen by the Commodity Futures Trading Commission. You open an account like a brokerage account, with ID checks, and trade in dollars. Which contracts you can trade can depend on your state: sports contracts in particular are contested in several states, and the list changes, so check Kalshi's own notices for where you live.
Polymarket started as an international, crypto-based exchange at polymarket.com, which doesn't allow US users to trade. It now also runs Polymarket US, a separate US-regulated exchange with its own accounts and its own list of markets. They share a name but not a market list or an account: a polymarket.com wallet and a Polymarket US account are different things.
Fees, with real numbers
Both platforms now use the same shape of fee: it's largest when a contract costs around 50¢ and shrinks toward 1¢ and 99¢, because it scales with price × (1 − price).
- Kalshi charges a fee on the expected earnings of each trade. On a standard market that works out to roughly 1.75¢ per contract at 50¢, so about $1.75 on 100 contracts. Some markets carry different fees, and some charge makers (orders that wait on the book) as well as takers. Cancelling a resting order is free.
- Polymarket (polymarket.com) charges takers only, using contracts × rate × price × (1 − price), with a rate that depends on the category, from 0.04 for politics, finance and tech to 0.07 for crypto. Makers are never charged and can earn rebates, and geopolitics markets carry no fee. In a 0.05-rate category, 100 contracts bought at 50¢ by a taker cost $1.25 in fees.
So on a typical trade at a middling price, Polymarket is usually a little cheaper, and much cheaper if you place limit orders that wait to be filled. Near the extremes (a 95¢ favorite, a 4¢ long shot) both fees get small. Fee schedules change; check each platform's fee page before you rely on a number.
Moving money in and out
Kalshi works in US dollars: deposits by bank transfer or debit card, and it also takes crypto deposits. polymarket.com works in USDC, a dollar stablecoin, held in a crypto wallet; Polymarket charges nothing to deposit or withdraw, though whoever you buy USDC through may. If you've never used a crypto wallet, Kalshi will feel more like a normal finance app.
How markets resolve
On Kalshi, each market has a written rulebook entry that says exactly what counts as Yes, with a named source, and Kalshi settles it. On polymarket.com, a result is proposed and can be disputed through UMA, an outside oracle, before the market settles.
The practical point: two markets on the "same" event can have different rules. One might settle on the official result, the other on a specific news source or deadline. When prices on the two platforms disagree, different rules are often why. Read both before assuming they're the same bet.
Which one should you use?
Mostly, where you live decides it: in the US, the choice is Kalshi or Polymarket US, since polymarket.com isn't open to US traders. Beyond that, plenty of people use more than one, for different markets or for a better price on the same event.
If you trade on both
The hardest part of trading on two platforms isn't the trading. It's knowing how you're actually doing. Each app shows its own balance and its own history, in its own way, and the number that matters, your total, lives in neither.
That's what Kesin is for. It's an independent iPhone app that keeps one book for both: your open positions with live P&L, your finished trades imported from each exchange, and Leaks, plain-English findings on where your money actually goes. You can log a bet from Kalshi, polymarket.com or Polymarket US in seconds, by searching or pasting its link. Or connect, and it fills itself in: Kalshi through a read-only API key (Kesin refuses a key that can trade, and you can disconnect at any time), Polymarket through your public polymarket.com wallet address. Polymarket US accounts can't connect yet. Kesin doesn't place trades or give picks.
See Kalshi and Polymarket in one place.
Free on the App Store, with an optional Premium plan.
More guides
Sources
- Kalshi Help Center, Fees (April 2026).
- Polymarket Documentation, Fees and Maker rebates.
- Kalshi and Polymarket change their rules, fees and availability often. This page was checked on October 10, 2026; the platforms' own pages are authoritative.