Kalshi vs Polymarket Liquidity 2026: 357 Books
Kalshi vs Polymarket liquidity read off 357 matched game books: the quote is good for $391 on Kalshi and $122 on Polymarket, and size flips 64 of them.
Affiliate disclosure: contains affiliate links; we may earn a commission at no extra cost to you. We have no commercial relationship with Kalshi. 18+ only — see BeGambleAware.org. Last updated 31 October 2026.
Key takeaways
- The quoted price is good for three times more money on Kalshi. Across 357 matched contracts on 156 games in 11 leagues, the median best ask held $391 on Kalshi against $122 on Polymarket — and $1,837 against $351 within a cent of it.
- Buy 1,000 contracts and Kalshi was cheaper on 61.6% of them, Polymarket on 20.4%. Median slippage: 0.00c against 0.87c. Half of Kalshi's 1,000-lots filled entirely at the quote, against a third of Polymarket's.
- Size reversed the cheaper venue on 64 contracts. Polymarket showed the better ask on 88, and on 46 of those Kalshi was still cheaper for a 1,000-lot. Another 61 were level on price and decided by depth alone.
- Every reversal was in a thin book. On the 150 contracts where both venues held $100-plus at the quote, none flipped: the quote is honest exactly when there is money behind it.
- The hole is league-specific, not venue-specific. Polymarket's median NHL book held $3.52 at the best ask; Kalshi's MLS book held $17 and slipped 18.7c on a 1,000-lot.
On this page
Every comparison of these two exchanges tells you to check the order book before you size a trade, and none tells you what you will find when you do. That matters more than the price: the two venues quote the same game within a cent of each other, so the money is not in the number on the button but in how much of it you can have. So we measured Kalshi vs Polymarket liquidity the only way it can be measured — pulling both full order books for the same contract within a second of each other, 357 contracts across 156 games and 11 leagues, then walking each book to price a real order. The quote is good for $391 on Kalshi and $122 on Polymarket, and on 64 contracts size reversed which venue was cheaper.
What we measured, and how the books were paired
We took every open game market in Kalshi's eleven league series — NFL, NBA, NHL, college football, the Premier League, La Liga, Serie A, Bundesliga, Ligue 1, the Champions League and MLS — and paired each fixture to its Polymarket game event by date and both teams' codes: 156 games, 357 contracts, one per team on two-way games and all three on soccer.
For each contract we pulled Kalshi's full order book and Polymarket's full CLOB book back to back, so the two venues were read a median 0.71 seconds apart and never more than 4.1 seconds apart. The whole sweep ran between 18:48:01 and 18:55:42 UTC on 31 October 2026. Then we walked the ask side of each book, level by level, and priced three orders: 100 contracts, 1,000 contracts and 5,000 contracts.
Prices here are what a taker pays before fees, which differ by venue and league, so fees stay out of every table below rather than mix two bases in one number; our Kalshi fees by market and Polymarket fees pieces do that arithmetic. One fee fact is still live: Polymarket reported zero_fees on all 52 NBA contracts, 0.03 on the 88 NFL and college football ones and 0.05 on the other 217 — the same three-schedule split as two days earlier, against docs listing one rate.
What the quoted price is actually good for
This is the number nobody publishes. A price with $4 behind it and a price with $4,000 behind it look identical on a screen, and they are not the same product.
Ask-side depth only, both books read within a median 0.71s of each other, 31 October 2026. Medians across all 357 matched contracts; the ratio column divides the two medians and is not a per-contract average.
Kalshi held more at the best ask on 232 of 357 contracts (65.0%), and the gap widens down the book: it quotes more levels and keeps more on each, so within a cent of the quote its median book was five times Polymarket's.
The deepest single quote was Kalshi's New England wins ask on 1 November: 2,065,644 contracts at 76c, about $1.57m at one price level, a figure Kalshi reports itself in yes_ask_size_fp. Polymarket's book held $16,219 at the same 76c. Both are real markets; they are not the same size of market.
The thin end is thinner than the medians suggest: nearly half of Polymarket's quotes had under $100 behind them and 103 had under $10, a quote you could clear with a bar tab. Kalshi has the same problem in fewer places — 79 contracts.
Kalshi vs Polymarket liquidity once you size up
Depth only matters through what it costs you, so we walked each book with three order sizes and measured the average fill price against the quote. Slippage below is in cents per contract on a $1 contract.
Slippage is the average fill price minus the best ask, walking the resting asks in price order. Pre-fee. "Cheaper fill" shares do not sum to 100% because the remaining contracts filled at the same average price on both venues.
Two things fall out. The first is that almost everything fills: both venues absorbed 1,000 contracts on every contract in the sample, and 5,000 on more than 96%. That is the trap, because filling is not filling cheaply. Polymarket books carry big resting asks up at 84c, 97c and 99c, so a market order never bounces — it completes at a price nobody would accept deliberately.
The second is that the median hides the shape. At 1,000 contracts both sit near zero for the typical liquid contract, while the 90th percentile is 15c on Kalshi and 17c on Polymarket. Liquidity here is not a level but a cliff: either thousands of dollars at the quote and you pay nothing, or $3 and you pay a fifth of the contract.
When the cheaper quote is the dearer fill
Here is the practical finding. Polymarket showed the better ask on 88 of the 357 contracts, and on 46 of those Kalshi was still cheaper once you bought 1,000. Shopping the displayed price picked the wrong venue in more than half the cases where it favoured Polymarket.
Three matched contracts from the 31 October sweep: an NHL reversal, a tie at the quote broken by depth, and an MLS reversal running the other way. Bold is the cheaper venue in that row pair. Pre-fee.
The Pittsburgh line is the whole article in one row. Polymarket showed 49c against Kalshi's 53c, a four-cent saving on the button, with $2 behind it. Buy a thousand and Polymarket averages 72.0c against Kalshi's 54.0c: the four-cent discount becomes an eighteen-cent penalty.
Charlotte is the same mistake in Kalshi's direction, and worse: a 19c ask with under a dollar behind it fills a 1,000-lot at 78.1c against Polymarket's 66.8c. Edmonton shows the case the screen cannot show at all — both quoted 66c, but one had $2,080 there and filled the lot at 66c while the other had $3 and averaged 82.7c. 61 contracts here were priced identically and decided entirely by depth.
Across the sample, 1,000 contracts changed the answer on 64 contracts, the quote-level winner held on 168, and the rest were level at both stages. At 5,000, 74 flipped.
Where the reversals live, and where the quote is honest
This is the part that makes the finding usable rather than alarming, and it took re-cutting the sample to see. Restrict the data to the 150 contracts where both venues held $100-plus at the best ask — 42% of the sample, 85 games, every league represented — and the reversals vanish.
On the 150 contracts with $100-plus at the quote on both venues, buying 1,000 contracts reversed the cheaper venue zero times.
Median slippage was 0.00c on both. The 90th percentile was 0.05c on Kalshi and 0.81c on Polymarket. Kalshi was cheaper on 44%, Polymarket on 14%, and 42% came out level. Every one of the 64 reversals in the full sample came from a book with less than $100 showing — which is also where 61 of the 91 remaining price-ties were broken by depth.
So the rule is not that the displayed price lies. It is that the price is only as informative as the money behind it, and on these exchanges that money is absent about half the time. Above a hundred dollars at the quote, shop the price and you will be right. Below it, the price is a suggestion.
League by league: the NHL hole and the MLS hole
The venue-level medians are an average of two very different maps. Neither exchange is thin everywhere, and the places where each one is thin do not overlap.
Medians per league, ask side, 31 October 2026. Ligue 1 (6 contracts) and Bundesliga (3) are in the totals but too small to rank here. Pre-fee.
Polymarket's NHL coverage is the most striking result in the sweep. It quoted all 68 contracts and its median best ask held $3.52, with 59% of NHL quotes under $10. Kalshi's median on the same games was $610, filling a 1,000-lot with no slippage at all. If you bet hockey, one of these is a price list and the other is a market.
MLS and Serie A run the other way: Kalshi's MLS books held a median $17 and cost 18.7c of slippage on a 1,000-lot against Polymarket's 9.7c, and Serie A is bad on both, worse on Kalshi. The NFL is where both are unambiguously real, and the soccer Polymarket actually trades — Premier League, Champions League, La Liga — fills cleanly on both.
One more asymmetry: 121 Polymarket markets (33.9%) had never traded at all, against 44 (12.3%) on Kalshi. A quoted market with no trading history is a placeholder, and the depth table is what that looks like from the taker's side.
The spread is not the depth, and it misleads here
If you judge liquidity by the bid-ask spread — which is what most guides, and most screens, encourage — you get the opposite answer to the one the fills give.
Polymarket's median spread was 1 cent against Kalshi's 2 cents. Polymarket was the tighter book on 30.3% of contracts, Kalshi on 33.6%, and they were level on the remaining 36.1%. On spread alone you would call this a draw, or a narrow Polymarket win.
Then you buy something. Kalshi filled half of all 1,000-lots with zero slippage against Polymarket's third, and was cheaper on three times as many contracts. A one-cent spread with $3 inside it is a tighter quote than a two-cent spread with $2,080 inside it, and it is a worse market. The spread tells you what the last contract costs; depth tells you what the next thousand cost, and only one of those is the trade you are making.
Can you actually trade $10,000 on these books?
You will see the claim that depth on these exchanges is fine for orders up to about $10,000, and the better comparison guides hedge it sensibly — one puts it as "both are deep at the top of their major markets and thin in the long tail". We can now put a number on it, by spending exactly $10,000 down each book.
"Absorbed" means the resting asks were sufficient to spend the full $10,000 at any price. Slippage is the average fill price minus the best ask. Pre-fee, 31 October 2026.
So the claim is true and useless at once. Kalshi takes $10,000 on nine contracts in ten — at a median ten and a half cents a contract, which on a 50c contract is a fifth of the stake handed to the book. The honest version is the last row: where there is real money at the quote a $10,000 order costs well under a cent on either venue, and everywhere else the size is available but the price is not.
The failures are league-shaped again. Polymarket could not absorb $10,000 where Kalshi could on 97 contracts, mostly college football: its entire ask side on Alabama wins was $4,469. The reverse happened on seven.
How to check depth before you click
Everything above reduces to one habit: read the size next to the price. The relationship is tight enough to use as a rule of thumb.
Median slippage on a 1,000-contract order, grouped by how much money was resting at the best ask. Same 357 contracts. Pre-fee.
Four rules. Read the depth at the quote first: above $1,000 showing, a thousand contracts costs nothing on either venue; under $10, five to eight cents. Use limit orders in the thin leagues — that night, hockey on Polymarket and MLS on Kalshi — where you are the liquidity and should be paid for it. Price your actual size, not one contract. And check both books even when prices agree: 61 contracts here were level on price and decided by what stood behind it.
For the single-venue version, our Polymarket slippage study walked 897 books and found the quote good for a median $197 across all categories — the sport subset is what this piece has now measured against a competitor.
Read the size before you take the price
The two venues quoted these games within a cent of each other, and a 1,000-contract order still came out cheaper on one of them 61.6% of the time. The depth at the quote is the part the screen makes easy to miss.
Visit Polymarket.com →Affiliate link to Polymarket; we have no commercial relationship with Kalshi. 18+ only. Polymarket restricts access from the United States, Canada and other listed jurisdictions. Prediction markets carry a substantial risk of loss. Nothing here is financial advice.
My verdict on Kalshi vs Polymarket liquidity
On the books we read, Kalshi is the deeper venue for sport and it is not close: three times the money at the quote, five times within a cent of it, half of all 1,000-lots filling with no slippage, and the cheaper fill on 61.6% of contracts. Polymarket's answer is a tighter headline spread, the least useful liquidity statistic there is.
But the venue-level answer is the wrong question, which I did not expect going in. Both exchanges are fine in the leagues they actually trade and close to unusable outside them, and the lists differ: hockey is a Kalshi league, MLS a Polymarket one, on the same night and by a bigger margin than the venue averages. Pick the league, then the venue, then read the number next to the price — and for the price comparison rather than the depth one, we measured 626 matched quotes two days earlier and they agreed to half a cent.
Related guides
- Kalshi vs Polymarket Odds 2026: 626 Prices — the price half of this question, measured two days earlier.
- Polymarket Slippage 2026: 897 Books Measured — the single-venue version, across every category.
- Kalshi Fees by Market 2026: 195 Exceptions — the fee this article deliberately leaves out of its tables.
- Polymarket Fees 2026: What You Actually Pay — why the published rate is a coefficient, not a percentage.
- Polymarket vs Kalshi 2026: Fees, Access and Who Settles — the platform decision, access rules included.
- Polymarket Arbitrage 2026: What Survives Costs — why thin-book gaps are not free money.
Kalshi vs Polymarket liquidity FAQ
Which has better liquidity, Kalshi or Polymarket?
Kalshi, on the sport we measured. Across 357 matched contracts its median best ask held $391 against Polymarket's $122, it filled half of all 1,000-contract orders with no slippage against Polymarket's third, and it was cheaper on 61.6%. The exception is league-level: Polymarket is deeper in MLS and Serie A.
How much can I buy at the quoted price?
A median of $391 on Kalshi and $122 on Polymarket, though the spread matters more than the median: 22.1% of Kalshi quotes and 28.9% of Polymarket quotes had under $10 behind them. Read the size on the contract you want, not a venue-wide figure.
Does the cheaper price always mean the cheaper trade?
No. Polymarket had the better ask on 88 of 357 contracts and Kalshi was still cheaper for a 1,000-contract order on 46 of them. Another 61 were quoted at the same price on both venues, where depth alone decided the fill.
How much slippage should I expect on a 1,000-contract order?
Nothing at all if the quote has over $1,000 showing, on either venue. Between $100 and $1,000, the median was 0.09c on Kalshi and 0.44c on Polymarket; under $10, 4.87c and 8.02c. The money at the quote predicts the cost better than the venue does.
Can you trade $10,000 on a prediction market game contract?
Usually yes, rarely at a sane price. Kalshi's books absorbed $10,000 on 92.2% of contracts and Polymarket's on 66.9%, but the median cost was about 10.5 cents a contract on both. On contracts with $100-plus at the quote, the same order cost under a cent.
Why is Polymarket's NHL book so thin?
We can only report what it showed: a median $3.52 at the best ask across 68 NHL contracts, 59% under $10, and a third of all matched Polymarket markets with no trading history. The quotes exist on every game; the money behind them does not. Kalshi's median on the same games was $610.
Is a tighter spread a sign of better liquidity?
Not on this evidence. Polymarket's median spread was 1 cent against Kalshi's 2 cents, yet Kalshi filled large orders more cheaply on three times as many contracts. A one-cent spread holding $3 is tighter and worse than a two-cent spread holding $2,000.
Do fees change the answer?
They can, where the depth difference is small, which is why they are out of these tables. Polymarket reported three sports schedules on the day — zero on NBA, 0.03 on NFL and college football, 0.05 elsewhere — so read the fee off the market itself. Our fees articles do that arithmetic.
Method and sources
Sample. All open markets in Kalshi's eleven league game series on 31 October 2026 (1,055 markets, 465 two-sided fixtures), paired to Polymarket game events by date and both teams' codes, resolving 156 games and 357 contracts: 68 NHL, 52 NBA, 48 college football, 45 Serie A, 40 NFL, 38 MLS, 24 Premier League, 18 La Liga, 15 Champions League, 6 Ligue 1, 3 Bundesliga.
Books. Kalshi's order book endpoint returns bids only, in an orderbook_fp object whose yes_dollars and no_dollars arrays are [price_dollars, count_fp] string pairs, so a YES ask is $1.00 minus a NO bid. We checked that against Kalshi's own yes_ask_dollars and yes_ask_size_fp: 354 of 357 matched on price and 344 on size exactly, the rest books that moved between calls 0.3s apart. Polymarket's /book was read per token and sorted before walking, because the live response served asks in descending price order, not the ascending order the docs specify, and because bestAsk on a two-outcome market refers to the first outcome, not the token requested.
Pricing. Slippage is the average fill price of a market order walking the resting asks, minus the best ask, in cents per $1 contract. Pre-fee, taker-side, buy side only. Bucket cuts use each book's own depth as read, not Polymarket's liquidityNum, which came from a listing call fifteen minutes earlier.
Four caveats. One eight-minute snapshot on a Saturday evening, NFL a day away and some MLS and college football already in play, so the thin tails would move on another night even if the venue ordering would not. Resting size is not a guarantee: orders cancel, and a book walked on paper is not a book filled. Contracts within a game are not independent, and soccer contributes three per fixture. And depth is half of execution cost; the fee is the other half and is in no table here. Nothing here is financial advice.
- Kalshi docs: Orderbook Responses — "Kalshi's orderbook only returns bids, not asks", and the
orderbook_fpshape. - Kalshi API changelog — the dollar and fixed-point field migration, including
liquidity_dollarsremoved on 1 October 2026 in favour ofyes_ask_size_fp. - Polymarket docs: Get order book — the
/bookresponse, its price and size strings, and the documented ask ordering. - Polymarket docs: Fees —
fee = C × feeRate × p × (1 - p), Sports listed at a 0.05 taker rate, and "Makers are never charged fees". - StartPolymarket: Polymarket vs Kalshi — the conventional view, and the advice this article tries to make actionable: "Check the order book of the specific market before you size a trade."