Polymarket and Kalshi both trade yes/no contracts that pay $1 if the event happens, but Kalshi is a CFTC-regulated US exchange, while polymarket.com is an international site on the Polygon blockchain and US residents use the separate Polymarket US app. This page compares two matching markets on price, spread, order-book depth, estimated fill and settlement rules, using public data with capture times.
The compare workbench puts one Polymarket market and one Kalshi market side by side: the current best bid and ask, the spread, 24-hour volume, the top five visible levels of each order book, a fill estimate for a chosen order size, and the full settlement rules of both. You pick the two markets by pasting their links or IDs, or by opening one of the curated pairs that PolyKal has checked by hand. Everything shown is a snapshot of public data with its capture time printed on the page; PolyKal is a read-only research tool and does not route orders.
A matching title is not enough. Two contracts are only worth comparing on price if they settle on the same fact, from the same source, at the same time. Before reading any spread, check five things in the rules of both markets: the exact question and any threshold or date in it; the resolution source (an official statement, a data release, a scoreboard); the settlement date and time, including time zone; how each outcome is defined (a Yes/No contract versus one candidate in a multi-outcome event); and how ties, postponements and cancellations are handled. Polymarket and Kalshi often list the same headline with different fine print, and the fine print is what settles.
PolyKal does not decide that two markets are the same bet. The “suspected matching events” list is produced by title similarity and settlement-time proximity and is shown only as a set of candidates. Treat it as a reading list, not a verdict.
Both platforms quote in cents for a contract that pays $1 if the outcome happens, so a price of 62¢ can be read as roughly a 62% implied probability. The best bid is what a buyer is currently willing to pay; the best ask is what a seller is asking; the spread between them is the immediate cost of crossing the book. A one-cent difference between platforms is well inside typical spreads and fees and usually means nothing. Kalshi markets with several candidates are quoted per candidate; PolyKal shows the Yes side of the selected candidate and derives the No side as 100 minus that price, which is how the exchange itself prices the pair.
The order-book panels list the five best price levels on each side with the quantity resting at each. The fill estimate walks those levels for the selected side and order size ($1K, $5K, $10K or $50K) and reports the average price you would have paid, how much of the order the visible depth could absorb, and the slippage against the top quote. If the five visible levels cannot absorb the order, the estimate says so and the average is computed only on the filled part. It does not model hidden liquidity, orders arriving after the snapshot, or levels beyond the five shown.
Fees change the answer more than most spreads do. Kalshi charges takers 0.07 × contracts × price × (1 − price), multiplied by a per-series factor published in its API (1 by default, 0 on fee-free series, 0.5 on some sports series) and rounded up to the cent per price level. Polymarket charges takers a rate that depends on the market's category (from 0 to 0.07) using the same price × (1 − price) shape, and charges makers nothing. PolyKal computes the fee for the estimated fill on each platform and shows the after-fee cost per share, which is the number to compare. The fee calculator and the two fee pages give worked examples.
Pages are rebuilt about every 15 minutes, and the order books can be re-queried by the visitor with a 10-second cooldown; the timestamp next to each book says when it was fetched. All times are US Eastern. A spread you see here is a spread that existed at that moment on the public book, not a price you can still trade.
A price gap between two markets is a fact about two order books at one moment. It is not a trading recommendation and it is not an arbitrage: the two contracts may settle on different terms, the gap may be smaller than the combined spreads and fees, and moving money between platforms takes time during which prices move. PolyKal shows the gap, the depth behind it and the cost of crossing it so that you can judge for yourself. It does not tell you what to buy.
Kalshi's standard taker rate is 7%, adjusted by a per-series multiplier (1 by default); Polymarket’s taker rate is set per market by category and is often lower, and Polymarket never charges makers. Neither charges a settlement or membership fee. As of 2026-09-12.
| Aspect | Kalshi | Polymarket |
|---|---|---|
| Taker fee | 7% × contracts × price × (1 − price), rounded up to the cent on each fill | Category-based, 0%–7% × shares × price × (1 − price) |
| Maker fee | Free on standard series; 1.75% on flagged series | Always free |
| Most expensive point | 1.75¢ per contract at 50¢ | 7% (crypto) |
| Settlement / membership fee | None | None |
| Published vs on-chain | Published rate is the official schedule | Declared per market in the API; some categories also checked against on-chain deductions |
Kalshi verified 2026-09-12; Polymarket verified 2026-09-20. Numbers from the PolyKal fee dataset (/data/fees.json).
| Polymarket category | Declared taker fee |
|---|---|
| Crypto | 7% |
| Sports | 5% |
| Economics | 5% |
| Culture | 5% |
| Weather | 5% |
| Other | 5% |
| Politics | 4% |
| Finance | 4% |
| Tech | 4% |
| Mentions | 4% |
| Geopolitics | 0% |
Declared category rates as of 2026-09-20. Polymarket sets the fee per market, so some markets charge less; the fee schedule lists which are verified against real on-chain deductions. Makers pay nothing.
It depends on the market. On crypto both charge the same taker rate (7%). On most other categories Polymarket's taker rate is lower, and Polymarket never charges makers, while Kalshi charges makers only on flagged series. Because spread and depth usually cost more than the fee, compare the exact after-fee cost of a specific trade in the calculator. As of 2026-09-12.
Neither on fees alone — the taker rate is identical, 7% on both Kalshi and Polymarket. Choose on liquidity: which venue shows the tighter spread and deeper book for the specific market. As of 2026-09-12.
On fees, Polymarket — its politics taker rate is 4% versus Kalshi's 7%, and Polymarket never charges makers. Kalshi may still win on a given market if its book is tighter or deeper. As of 2026-09-12.
Polymarket never charges makers. Kalshi charges makers nothing on standard series and 1.75% only on the series it flags for maker fees; takers pay on both platforms. Resting limit orders are the cheapest way to trade on either venue. As of 2026-09-12.
The compare workbench puts one Polymarket market and one Kalshi market side by side: the current best bid and ask, the spread, 24-hour volume, the top five visible levels of each order book, a fill estimate for a chosen order size, and the full settlement rules of both. You pick the two markets by pasting their links or IDs, or by opening one of the curated pairs that PolyKal has checked by hand. Everything shown is a snapshot of public data with its capture time printed on the page; PolyKal is a read-only research tool and does not route orders.
A matching title is not enough. Two contracts are only worth comparing on price if they settle on the same fact, from the same source, at the same time. Before reading any spread, check five things in the rules of both markets: the exact question and any threshold or date in it; the resolution source (an official statement, a data release, a scoreboard); the settlement date and time, including time zone; how each outcome is defined (a Yes/No contract versus one candidate in a multi-outcome event); and how ties, postponements and cancellations are handled. Polymarket and Kalshi often list the same headline with different fine print, and the fine print is what settles.
PolyKal does not decide that two markets are the same bet. The “suspected matching events” list is produced by title similarity and settlement-time proximity and is shown only as a set of candidates. Treat it as a reading list, not a verdict.
Both platforms quote in cents for a contract that pays $1 if the outcome happens, so a price of 62¢ can be read as roughly a 62% implied probability. The best bid is what a buyer is currently willing to pay; the best ask is what a seller is asking; the spread between them is the immediate cost of crossing the book. A one-cent difference between platforms is well inside typical spreads and fees and usually means nothing. Kalshi markets with several candidates are quoted per candidate; PolyKal shows the Yes side of the selected candidate and derives the No side as 100 minus that price, which is how the exchange itself prices the pair.
The order-book panels list the five best price levels on each side with the quantity resting at each. The fill estimate walks those levels for the selected side and order size ($1K, $5K, $10K or $50K) and reports the average price you would have paid, how much of the order the visible depth could absorb, and the slippage against the top quote. If the five visible levels cannot absorb the order, the estimate says so and the average is computed only on the filled part. It does not model hidden liquidity, orders arriving after the snapshot, or levels beyond the five shown.
Fees change the answer more than most spreads do. Kalshi charges takers 0.07 × contracts × price × (1 − price), multiplied by a per-series factor published in its API (1 by default, 0 on fee-free series, 0.5 on some sports series) and rounded up to the cent per price level. Polymarket charges takers a rate that depends on the market's category (from 0 to 0.07) using the same price × (1 − price) shape, and charges makers nothing. PolyKal computes the fee for the estimated fill on each platform and shows the after-fee cost per share, which is the number to compare. The fee calculator and the two fee pages give worked examples.
Pages are rebuilt about every 15 minutes, and the order books can be re-queried by the visitor with a 10-second cooldown; the timestamp next to each book says when it was fetched. All times are US Eastern. A spread you see here is a spread that existed at that moment on the public book, not a price you can still trade.
A price gap between two markets is a fact about two order books at one moment. It is not a trading recommendation and it is not an arbitrage: the two contracts may settle on different terms, the gap may be smaller than the combined spreads and fees, and moving money between platforms takes time during which prices move. PolyKal shows the gap, the depth behind it and the cost of crossing it so that you can judge for yourself. It does not tell you what to buy.
Kalshi's standard taker rate is 7%, adjusted by a per-series multiplier (1 by default); Polymarket’s taker rate is set per market by category and is often lower, and Polymarket never charges makers. Neither charges a settlement or membership fee. As of 2026-09-12.
| Aspect | Kalshi | Polymarket |
|---|---|---|
| Taker fee | 7% × contracts × price × (1 − price), rounded up to the cent on each fill | Category-based, 0%–7% × shares × price × (1 − price) |
| Maker fee | Free on standard series; 1.75% on flagged series | Always free |
| Most expensive point | 1.75¢ per contract at 50¢ | 7% (crypto) |
| Settlement / membership fee | None | None |
| Published vs on-chain | Published rate is the official schedule | Declared per market in the API; some categories also checked against on-chain deductions |
Kalshi verified 2026-09-12; Polymarket verified 2026-09-20. Numbers from the PolyKal fee dataset (/data/fees.json).
| Polymarket category | Declared taker fee |
|---|---|
| Crypto | 7% |
| Sports | 5% |
| Economics | 5% |
| Culture | 5% |
| Weather | 5% |
| Other | 5% |
| Politics | 4% |
| Finance | 4% |
| Tech | 4% |
| Mentions | 4% |
| Geopolitics | 0% |
Declared category rates as of 2026-09-20. Polymarket sets the fee per market, so some markets charge less; the fee schedule lists which are verified against real on-chain deductions. Makers pay nothing.
It depends on the market. On crypto both charge the same taker rate (7%). On most other categories Polymarket's taker rate is lower, and Polymarket never charges makers, while Kalshi charges makers only on flagged series. Because spread and depth usually cost more than the fee, compare the exact after-fee cost of a specific trade in the calculator. As of 2026-09-12.
Neither on fees alone — the taker rate is identical, 7% on both Kalshi and Polymarket. Choose on liquidity: which venue shows the tighter spread and deeper book for the specific market. As of 2026-09-12.
On fees, Polymarket — its politics taker rate is 4% versus Kalshi's 7%, and Polymarket never charges makers. Kalshi may still win on a given market if its book is tighter or deeper. As of 2026-09-12.
Polymarket never charges makers. Kalshi charges makers nothing on standard series and 1.75% only on the series it flags for maker fees; takers pay on both platforms. Resting limit orders are the cheapest way to trade on either venue. As of 2026-09-12.