The Quick Answer
One cent. That is the median bid-ask spread on Kalshi, measured across 9,554 live order books. It sounds like nothing, and on a coin-flip contract it very nearly is — a penny either side of a 50-cent price is noise.
On a longshot it is the whole game. On a contract trading under a dime, the typical spread is 40% of the price. You are not paying a penny; you are paying two fifths of what the contract is worth just to get in and out, before Kalshi's fees and before you are right or wrong about anything.
That is the finding, and it is the reason a strategy that looks profitable on paper at 4 cents usually is not.
The Number, And Exactly Where It Came From
We captured the full top of book — best bid, best ask, and the size behind each — on Kalshi's daily high-temperature markets, every few minutes, for two weeks.
| Order Books Captured | 9,554 |
| Distinct Markets | 1,984 |
| Days | 14 (2026-07-30 to 2026-08-12) |
| Series | Kalshi daily high temperature, 8+ US cities |
| Books With A Live Two-Sided Quote | 7,154 (74.9%) |
Across the 7,154 books that had both a bid and an ask:
- Median Spread: 1 Cent
- mean spread: 1.87 cents
- 90th percentile: 4 cents
- widest observed: 25 cents
- 63.7% Of Books Were Quoted Exactly 1 Cent Wide
So the headline is genuinely tight. Nearly two-thirds of the time, Kalshi's book is as tight as a book can be.
The Part That Matters: A Cent Is Not A Cent
A spread quoted in cents is flat. The thing you are buying is not. So the same one-cent spread is a completely different tax depending on where the contract trades.
| Contract Price | books | median spread | median spread as % of price |
|---|---|---|---|
| 1–9¢ | 5,500 | 1¢ | 40.0% |
| 10–24¢ | 1,642 | 1¢ | 8.7% |
| 25–49¢ | 12 | 1¢ | 3.8% |
⚠️ The 25–49¢ row rests on 12 books. Treat it as a direction, not a figure — these markets spend almost all their life priced under a quarter.
Read the right-hand column, not the middle one. Crossing the spread on a longshot costs about 4.6 times what it costs on a 10–24¢ contract, and roughly ten times what it costs at 25–49¢. Kalshi's own documentation — which explains perfectly well what a spread is and how to calculate one — does not tell you this, because it is a property of your position, not of the market.
If you buy a 5-cent contract at the ask and something goes wrong and you sell at the bid, you are down by that same fraction before the underlying event has moved at all.
The Other Cost Nobody Quotes: One-Sided Books
A quarter of the books we captured — 2,400 of 9,554, 25.1% — did not have a live quote on both sides. No bid, or no ask, or neither.
A spread statistic can only be computed when both sides exist, which means every published spread figure, including ours, is measured on the subset of moments when the market was actually working. The other quarter of the time the question "what is the spread" has no answer, and the practical answer to "can I get out right now" is no.
And when there is a quote, it is not always deep:
- Median Size At The Best Ask: 27 Contracts
- 10th percentile: 2 contracts
One book in ten is showing you a price good for two contracts. That is a real price — it is just not a price you can do anything with.
What This Number Does Not Tell You
Stated plainly, because a measurement without its limits is a slogan:
- This Is One Market Family. Kalshi's daily high-temperature series across eight-plus cities. Sports, politics and crypto markets have different maker activity and almost certainly different spreads. Do not quote this as "Kalshi's spread." Quote it as what it is.
- Fourteen Days. Late July into mid-August 2026. Spreads widen in volatility and around news; a fortnight of summer weather markets is a calm sample.
- Top Of Book Only. We measured the best bid and best ask. A larger order walks the book and pays more than the headline spread — the size figures above are the hint at how much more.
- It Is A Snapshot Series, Not A Tape. We sampled every few minutes. Between two snapshots the book moves, so this describes what a trader looking at the screen would typically see, not every price that ever existed.
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How To Use It Before You Trade
- Convert the spread to a percentage of the price you are paying. Every time. A 1-cent spread on a 6-cent contract is a 17% round trip; the same penny on a 60-cent contract is 1.7%.
- Check both sides are actually quoted before you assume you can exit. One book in four here was not two-sided.
- Look at the size, not just the price. A 1-cent spread good for two contracts is not a 1-cent spread for anyone trading real money.
- Add Kalshi's fees on top. The spread is what the market charges you. The fee schedule is separate, and it scales with price.
