Polymarket vs Kalshi: Cheaper Fees, Sharper Prices

Polymarket is cheaper than Kalshi on sports, and by less than almost every comparison claims. Both exchanges charge the identical fee shape, so the whole cost question reduces to one number: Kalshi's published taker rate of 0.07 against Polymarket's 0.05 on sports. That works out to a gap of half a percentage point of break even on a coin flip. Meanwhile the choice between a market order and a resting limit order is worth 3.5 times as much on the same trade. Here is what each price really costs you.

The same formula, one different number

Most Polymarket vs Kalshi comparisons put two incompatible numbers side by side, a per contract fee against a percentage of notional, and the reader has no way to reconcile them. The comparison is far simpler than that, because both exchanges publish the same formula.

Kalshi charges takers 0.07 x contracts x price x (1 - price). Polymarket charges takers rate x contracts x price x (1 - price), where the rate depends on the market's category. Same shape, same curve, one coefficient apart.

That shape means the fee peaks at a 50 cent contract and falls away symmetrically toward both ends, so a 30 cent contract and a 70 cent contract cost exactly the same to trade. It is a deliberate design: the exchange charges most where the outcome is most uncertain and least where a contract is nearly settled.

Polymarket's published rate is not one number, it is a table by category. Sports sits at 0.05, crypto at 0.07, politics and finance and tech at 0.04, economics and culture and weather at 0.05, and geopolitics at 0. Kalshi applies 0.07 across the board on standard markets.

So the honest headline is narrower than "Polymarket is cheaper". Polymarket is cheaper than Kalshi on sports, identical on crypto, and cheaper still on politics. The advantage is a property of the category you are trading, not of the platform.

Why the fee gap never narrows

Because both fee curves are the same shape scaled by a different constant, Polymarket's sports fee is 5/7 of Kalshi's at every single price. Not roughly, and not only near a coin flip. Exactly 5/7, at 20 cents and at 95 cents alike.

This is where the common claim that "the gap narrows at the extremes" goes wrong. The gap in cents narrows, because both fees shrink toward the tails. The gap in proportion does not move at all. Polymarket is 28.6% cheaper on sports wherever you look.

Read the last column, because that is the one that decides bets. Half a point of break even at a coin flip, shrinking to under a fifth of a point on a heavy favorite. In American odds, a flat 50 cent contract is about −107 on Kalshi and about −105 on Polymarket sports.

Maker versus taker is the bigger lever

Both exchanges publish a zero maker fee on standard markets. A limit order that rests on the book and gets filled by someone else pays nothing on either platform.

That single fact outweighs everything above. On a 50 cent sports contract, taking the price costs you 1.75 points on Kalshi and 1.25 points on Polymarket. Resting an order costs zero on both. So going from taker to maker saves the full 1.75 points on Kalshi, which is 3.5 times the 0.50 point gap between the two exchanges.

Stated plainly: resting a limit order on Kalshi is cheaper than taking one on Polymarket. If you are choosing a platform on fees alone, you are optimizing the smaller of the two variables.

The catch is that a resting order is not a filled order. You are trading a certain fee for uncertain execution, and in a moving market the price you wanted may be gone before anyone crosses to you. That trade is worth making when you have a view on a price and time to wait, and worth skipping when you are hitting a number that is about to move, which is the same line shopping judgement a sportsbook bettor makes about a price that is drifting.

Kalshi also applies a maker fee on a handful of very high volume events rather than its usual zero, and both exchanges revise their schedules. Confirm the live fee page for the specific market before you size a trade around this.

What the two really hold

Fees per contract are hard to feel. Effective hold, the same measure you would apply to a sportsbook, is not.

Take a two sided market with no spread, both sides priced at 50 cents, and both sides paying the taker fee. Each side's break even is 51.75% on Kalshi, so the two sum to 103.50% and the effective hold is about 3.4%. On Polymarket sports the sides break even at 51.25%, summing to 102.50% for a hold near 2.4%. A standard −110 sportsbook line implies 52.38% a side, sums to 104.76%, and holds about 4.5%.

Both exchanges undercut a standard sportsbook line, which is the real story, and they sit about a point apart from each other. That is a ladder worth knowing, and it is a much smaller spread than the "near zero vig" framing suggests. For the same treatment applied to a book instead of a rival exchange, see Kalshi vs sportsbook.

One asymmetry sits underneath the table. Kalshi rounds the fee on an order up to the next cent, while Polymarket rounds to five decimal places. On a large order that rounding disappears into the total. On a single contract at 50 cents it turns a 1.75 cent fee into 2 cents, a surcharge of 14% on the fee, and it widens the gap against Polymarket from 0.50 points to 0.75. Small orders pay disproportionately on Kalshi. Drop the contract count in the widget above to 1 and watch the round up line appear.

How you fund the account can erase the difference

The trading fee is not the only cost, and for many bettors it is not the largest one.

Kalshi funds in dollars and its ACH deposits and withdrawals are free. Polymarket's original exchange settles in USDC on chain, and getting dollars into USDC through a card onramp has historically cost somewhere in the range of 1% to 3%, with the exact figure set by the third party processor rather than by Polymarket.

Put that against the fee saving. Stake $100 at 50 cents and you hold 200 contracts. Kalshi's fee is $3.50, Polymarket sports charges $2.50, and you saved $1.00, or 1.0% of the stake. A single card deposit at 1% to 3% costs $1 to $3 on that same $100.

So one funding decision can cost more than the fee advantage on that money's first round of trades. The two are not the same kind of cost, and the comparison cuts both ways: the onramp is paid once per deposit while the fee is paid on every trade, so a bettor who deposits rarely and trades often still comes out ahead on total cost with Polymarket, and a bettor who tops up frequently in small amounts may not. Fund in the cheapest way each platform offers, and check the current options yourself, because the rails on both have changed more than once.

Kalshi has the sharper price

Cost is one axis. Price quality is a different one, and here the ranking flips.

We studied over 600 million MLB player prop line movements and 1.3 million closing market lines across every book and exchange we could track, and Kalshi posted the sharpest prices in the dataset, ahead of traditional sportsbooks including Pinnacle. Its side of a crossed market rarely left value on the table.

That matters far beyond Kalshi itself. A sharp price is the best available estimate of true probability, which makes it the number you want to devig and price everything else against. If you are hunting positive expected value at a soft sportsbook, the reference line you compare to determines whether your edge is real or imaginary, and no vig fair odds are only as fair as the source you built them from.

There is a useful consequence: pricing off Kalshi and then betting the softer sportsbook side can be worth more than trading the Kalshi contract at all, because the trading fee only applies to the leg you actually place on the exchange.

Polymarket has the readable flow

Polymarket's structural advantage is not its price. It is that you can see who is behind one.

Polymarket settles on chain, so every position is attached to a public wallet address and its full history is a matter of record. Kalshi runs a closed order book: you see the price, the depth and the volume, but never the participant. Two exchanges, two completely different information sets.

That asymmetry is why Prediction Insiders is a Polymarket product and could not be a Kalshi one. It continuously discovers Polymarket wallets with notable sports track records, currently 200+ and growing, shows each one's pregame return, sample size and consistency, and lets you choose which to follow. Every wallet you add is timestamped, so its resolved positions from that point form an out of sample forward test rather than a backtest you have to take on faith.

This is a genuinely different question from "what is the fair price". Sharp money analysis at a sportsbook is mostly inference: you watch a line move and reason backwards about who pushed it. On Polymarket the move and the mover are both visible.

Access, funding and the legal picture

Both exchanges operate as CFTC regulated venues rather than state licensed sportsbooks, and both are being contested at the state level. Kalshi has run as a designated contract market in the US for longer. Polymarket returned to the US market by acquiring the CFTC registered QCX exchange and clearinghouse in 2025, with a CFTC amended order of designation in November 2025 permitting QCX, doing business as Polymarket US, to operate.

Availability is genuinely patchy and it moves. Several states have pushed back directly, with cease and desist letters reported in Arizona, Connecticut, Massachusetts and Tennessee, and Minnesota passing a law criminalizing the operation of a prediction market. Federal court decisions have gone the exchanges' way more often than not so far, but nothing here is settled.

This page is general information and not legal advice. The only reliable answer for your state is the one each platform's own signup and geolocation check gives you, so check there before you plan around access. The same caution applies to fee schedules, funding rails and market coverage, all of which have changed on both platforms within the past year.

Which one should you use

Neither exchange wins outright, and the useful framing is per job rather than per platform.

• Cheapest sports execution: Polymarket, by 0.50 points at a coin flip, provided you can fund it cheaply.
• Best reference price to devig against: Kalshi, on the evidence of our own prop study.
• Reading who is on which side: Polymarket, because on chain settlement makes positions attributable.
• Simplest dollar in, dollar out: Kalshi, with free ACH and no stablecoin step.
• Cheapest execution of all, on either: rest a limit order and pay no fee at all.
• Small orders: Polymarket, since Kalshi's round up to the cent falls hardest on a handful of contracts.

The practical answer for most bettors who take this seriously is that these are complements, not rivals. Price off Kalshi, read the flow on Polymarket, and place the actual bet wherever the number is best, which is often a soft sportsbook rather than either exchange.

SmartStake is built for exactly that split. The prediction market converter turns either exchange's cent prices into American odds so you can compare them against a book on one scale, the Kalshi and Polymarket converter guides cover each in detail, Prediction Insiders reads the Polymarket wallet flow, and the devigging calculator turns whichever reference you trust into a fair line. The broader category, and how event contracts differ from a sportsbook in the first place, is covered in prediction market betting explained.

Frequently asked questions

Is Polymarket cheaper than Kalshi? Polymarket is cheaper than Kalshi on sports markets, but by less than most comparisons suggest. Both exchanges charge the same fee shape, rate x contracts x price x (1 minus price). Kalshi's published taker rate is 0.07 and Polymarket's sports rate is 0.05, so Polymarket's fee is 5/7 of Kalshi's at every price. At a 50 cent contract that is 1.25 cents against 1.75 cents, a gap of 0.50 percentage points of break even. On Polymarket crypto markets, where the published rate is also 0.07, the two charge the same.

What is the real vig on Polymarket and Kalshi? On a two sided market priced at 50 cents with no spread, both sides paying the taker fee works out to roughly 2.4% of effective hold on Polymarket sports and roughly 3.4% on Kalshi, against about 4.5% on a standard −110 sportsbook line. Both exchanges undercut a sportsbook, and the difference between them is around 1 point of hold, not the multiples that headline fee tables imply.

Does maker or taker matter more than which exchange I use? The maker choice is worth more than the platform choice. Both exchanges publish a zero maker fee on standard markets, so a resting limit order that gets filled pays nothing. On a 50 cent contract that saves the full 1.75 points on Kalshi, which is 3.5 times the 0.50 point gap between Kalshi and Polymarket sports. Resting an order on Kalshi costs less than taking one on Polymarket.

Which has sharper prices, Polymarket or Kalshi? Kalshi posted the sharpest prices in our study of over 600 million MLB player prop line movements, ahead of traditional sportsbooks including Pinnacle. That makes Kalshi the stronger reference price to devig against. Polymarket's advantage is different: it settles on chain, so individual positions are publicly attributable to wallets in a way Kalshi's closed order book is not.

Can you see who is betting on Polymarket? You can see who is betting on Polymarket, because it settles on chain and every position is attached to a public wallet address. Kalshi runs a closed order book, so you see the price and the volume but never the participant. SmartStake Prediction Insiders uses that asymmetry directly, tracking 200+ qualified Polymarket wallets and forward testing each one from the moment you add it.

The bottom line

Polymarket and Kalshi are one coefficient apart on cost, and much further apart on everything else. Polymarket charges 5/7 of Kalshi's fee on sports, holds about 2.4% against Kalshi's 3.4%, and settles on chain so you can see who holds what. Kalshi prices sharper, funds in dollars, and rounds fees up on small orders.

The number to remember is not either rate. It is that a resting limit order pays nothing on either exchange, which is worth 3.5 times more than the gap you were choosing between. Get the order type right first, then worry about the logo.