Kalshi vs Polymarket, with the actual prices
Most comparisons of these two venues are feature checklists written once and left alone. This one is the same contracts priced on both venues right now: the difference in percentage points, what is left of it after each venue’s own fees, and the volume and open interest standing behind each quote. Everything below is observed data with the time it was read printed on it.
The same contract on both venues
Matched and reviewed pairs only. The second numeric column is the one that matters: it is what remains of the difference once the fee assumption is applied to both sides.
01 Market snapshot
The Polymarket–Kalshi gap, before and after fees
The same matched contract on both venues, with the raw difference and what is left once each venue’s own fee is applied.
ObservedObserved 9 rowsWithin this table’s source-time freshness window; prices can change between observations.
| Meeting | Contract | PM − Kalshi (percentage points) | After venue fees (percentage points) | Polymarket 24h volume (USD) | Kalshi 24h volume (USD) | Kalshi open interest (USD) |
|---|---|---|---|---|---|---|
| September | 25 bp increase | 1 | 0 | 1,551,763 | 1,899,525 | 32,627,113 |
| September | No change | -2 | 0 | 2,205,884 | 1,899,525 | 32,627,113 |
| September | 25 bp decrease | -0.20 | 0 | 1,975,108 | 1,899,525 | 32,627,113 |
| October | 25 bp increase | 0 | 0 | 30,115.00 | 6,320.54 | 402,063.13 |
| October | No change | 1 | 0 | 6,046.00 | 6,320.54 | 402,063.13 |
| October | 25 bp decrease | -0.50 | 0 | 18,346.00 | 6,320.54 | 402,063.13 |
| December | 25 bp increase | -0.50 | 0 | 6,808.00 | 3,558.58 | 103,854.60 |
| December | No change | -3 | 1 | 4,334.00 | 3,558.58 | 103,854.60 |
| December | 25 bp decrease | -0.30 | 0 | 3,574.00 | 3,558.58 | 103,854.60 |
Scroll to see all columns.
CoverageOnly the reviewed Fed meeting and contract combinations shown. Prices are percentages of a $1 payout; a gap is not an executable return.
The after-fee column applies the source pack’s assumed fee of 2 percentage points across the pair. Real fees depend on your account, order type and the venue’s current schedule.
Volume and open interest are reported per meeting by each venue, not per contract row.
Depth, transfer time, settlement wording and account access are not in this calculation. A remaining gap is a reason to look, not an executable trade.
What Kalshi is quoting, and what stands behind it
Price is only half of a venue comparison. Traded volume says how much attention a contract is getting; open interest says how much money is already committed to an answer.
02 Market snapshot
Kalshi prices, volume and open interest by meeting
What Kalshi is quoting for each tracked Federal Reserve decision, with the traded volume and open interest behind the quote.
ObservedObserved 3 rowsWithin this table’s source-time freshness window; prices can change between observations.
| Meeting | Decision date | Kalshi: increase | Kalshi: no change | Kalshi: decrease | Kalshi 24h volume (USD) | Kalshi open interest (USD) | PM − Kalshi on the increase (percentage points) |
|---|---|---|---|---|---|---|---|
| September | 2026-09-16 | 77.5% | 22.5% | 0.5% | 1,899,525 | 32,627,113 | 1 |
| October | 2026-10-28 | 37.5% | 60.5% | 2.5% | 6,320.54 | 402,063.13 | 0 |
| December | 2026-12-09 | 57.5% | 42.5% | 3.5% | 3,558.58 | 103,854.60 | -0.50 |
Scroll to see all columns.
CoverageThe Federal Reserve meetings in Vultax’s Fed pack. Kalshi figures come from the venue; Vultax does not restate them.
Open interest counts contracts still outstanding; volume counts contracts traded in the window the venue reports. They answer different questions.
The three contracts on a meeting need not sum to 100: they are separate markets with their own spreads, and the pack takes each independently.
Kalshi is a US-regulated exchange with its own eligibility rules. Availability of a contract to you is a matter for the venue, not for Vultax.
Four differences that actually change a decision
The same question, written twice
Two venues rarely word a contract identically. The source of record, the cut-off time and the treatment of edge cases can all differ, and where they do, a price difference is a difference of definition rather than of opinion. Vultax only compares pairs that have been matched and reviewed as the same question with a compatible close, and the review travels with the pair.
Fees are charged differently, and both matter
Neither venue charges a flat percentage of notional. Fees on a contract priced between zero and one fall hardest in the middle of the range, which is exactly where the interesting disagreements sit. The after-fee column in the first table applies the pack's stated assumption to both sides; substitute your own from each venue's schedule and the picture changes.
Depth is per contract, not per venue
A venue can be deep on the next decision and almost unquoted on the one after it. That is why the tables carry volume and open interest per meeting: a two-point gap on a contract with a few thousand dollars of turnover is not the same finding as a two-point gap on one with millions.
One of them is visible on-chain
Polymarket positions settle on a public blockchain, which is why the largest trades and the trader leaderboards on this site exist at all: the flow is public. Kalshi publishes market-level data — price, volume, open interest — rather than per-wallet trading, so the trader analytics on Vultax are Polymarket-side.
Before you compare two prices
- Check that the two contracts settle on the same source, on the same date, with the same treatment of the awkward cases.
- Apply both venues' fees, from your own account's schedule rather than an assumed rate.
- Look at the size behind the quote before treating a difference as tradeable.
- Confirm the contract is available to you. Each venue sets its own eligibility rules, and that is a matter for the venue.
Venue facts on this page last checked . The tables above carry their own observation times and are newer.
Questions
Which is better, Kalshi or Polymarket?
They are different products more than they are competitors, and the honest answer depends on the contract. Read the rows above: on the meetings Vultax tracks the two venues usually agree within a point or two, and where they do not, the size behind the quote and the settlement wording matter more than the venue.
Do the two venues price the same event differently?
Frequently, by small amounts, and occasionally by more on thin contracts. The gap column shows the current difference in percentage points for the contracts that have been matched and reviewed as the same question.
Can I arbitrage the difference?
Rarely. The after-fee column strips out each venue's own fee assumption, and most differences do not survive it. On top of that you would need cleared funds on both venues, depth at the quote, and the contract to be available to you. The cross-venue page goes into why.
Which venue has more liquidity?
It varies by contract, which is why the tables carry volume and open interest per meeting rather than a single verdict. A venue that is deeper on the near meeting is often thinner on the far ones.
Are prediction market prices the same as probabilities?
They are prices for contracts that pay one dollar on a given outcome, so they are often read that way. They carry a spread and a fee, and on a thin contract they move on very little money. Vultax's published research measures how informative these prices have been on the venues it covers, with the window and the sample stated.
Where does Vultax get these numbers?
From the venues' own public market data, read on a single observation pass and republished with the time it was read. Every table on this page exports as JSON and CSV.
Does Vultax let me trade on either venue?
No. Vultax is research and simulation: it does not route orders, hold funds or connect to a venue on your behalf on any plan.