Kalshi fees explained: what you actually pay per trade

The fee formula

Kalshi charges a per-contract trading fee computed as roughly 7¢ × contracts × price × (1 − price), rounded up to the nearest cent. That is the single formula the entire fee schedule reduces to for the core exchange. The important insight is that fees are non-linear in price: they peak in the middle of the book, where price × (1 − price) is at its maximum of 0.25, and they approach zero at the extremes. A $0.50 contract is the most expensive point on the curve; a $0.05 or $0.95 contract costs almost nothing to trade.

Worked examples

100 contracts at $0.50: 7¢ × 100 × 0.5 × 0.5 = $1.75 total fee ($1.75 to buy, $1.75 to sell)
100 contracts at $0.10: 7¢ × 100 × 0.1 × 0.9 = $0.63 total fee
100 contracts at $0.90: 7¢ × 100 × 0.9 × 0.1 = $0.63 total fee (fees are symmetric around $0.50)
1,000 contracts at $0.30: 7¢ × 1000 × 0.3 × 0.7 = $14.70 total fee
10 contracts at $0.05: 7¢ × 10 × 0.05 × 0.95 = $0.03 total fee (rounded up from $0.033)

Why the curve is shaped that way

The math is not arbitrary. The variance of a binary outcome is p × (1 − p), so the fee is proportional to the variance of the contract. Contracts trading near $0.50 have the most uncertainty and, historically, the highest volume of speculative flow — Kalshi captures more fee revenue there without pricing out the low-probability tail markets that would otherwise be too expensive to trade. From a trader's perspective, the practical implication is that a scalp on a $0.50 market has to overcome roughly 3.5% round-trip friction, while a directional bet on a $0.10 tail contract has closer to 1.3% friction.

What's NOT a fee on Kalshi

Kalshi does not charge any of the following: deposit fees for ACH or debit card funding, ACH withdrawal fees, account maintenance fees, inactivity fees, market-data fees, or API access fees. There is no spread markup layered on top of the order book — what you see quoted is what fills, less the transparent per-contract fee above. The only friction beyond the fee formula is whatever spread exists between the best bid and best ask, which is a function of order-book depth on that specific market, not a Kalshi-imposed charge.

Fee promotions and waivers

Kalshi periodically runs promotional fee waivers on new contract categories to bootstrap liquidity. When a category is in a promotional window, fees on that specific category can be zero or heavily discounted — check the market details before assuming the standard formula applies. Some institutional market-maker programs also have negotiated fee schedules, but those are not available to retail traders and do not affect the public formula above.

How Kalshi's cost compares to a sportsbook

A standard −110 sportsbook line bakes approximately 4.5% vig into every wager. That vig is not disclosed as a fee — it is embedded in the odds themselves — but it is the effective cost of doing business. On a Kalshi market priced at $0.50, the round-trip fee cost works out to about 1.75% of notional, and on markets priced away from the middle it is meaningfully less. For a breakeven-skill trader, that difference is the difference between a losing year and a winning one.

How Kalshi's cost compares to Polymarket

Polymarket does not charge an explicit per-trade fee, but the total cost of a Polymarket round trip includes gas to approve USDC, gas to place and cancel orders, gas to redeem winning positions, and — for US-fiat-denominated traders — bridge fees to move USDC on and off Polygon. On small trades those fixed costs frequently exceed Kalshi's fee. On very large trades, Polymarket's near-zero variable cost pulls ahead. There is no single winner; the crossover point depends on trade size.

Estimating your true all-in cost before clicking Buy

The practical checklist is short. First, look at the mid-price and apply the formula — that gives you the exchange fee. Second, look at the spread between best bid and best ask and assume you pay half the spread as slippage on a market order. Third, if you are trading size relative to the book depth, add expected impact. The sum of those three is your true entry cost, and you double it for the round-trip exit. If the mid is $0.50 and the spread is 2¢, expect roughly 3.5% + 2% = 5.5% round-trip friction — you need edge greater than that to make money.

FAQ

Are Kalshi's fees higher than a sportsbook?

No — Kalshi is meaningfully cheaper than a standard −110 sportsbook line. A −110 line bakes in roughly 4.5% vig on every wager; a Kalshi trade at $0.50 costs about 1.75% of notional round-trip, and less at prices away from the middle. For anyone who bets seriously, the difference compounds into a real edge over the course of a year.

Why do fees peak at $0.50 instead of being flat?

Because the fee formula is proportional to p × (1 − p), which is the statistical variance of a binary outcome. That expression is maximized at $0.50 and approaches zero at the extremes. Kalshi captures more fee revenue where uncertainty and volume are highest, while keeping tail markets cheap enough to remain tradeable. From a trader's view, low-probability contracts are effectively fee-free.

Does Kalshi charge to deposit or withdraw?

No. Standard ACH deposits and withdrawals are free, debit-card deposits are free, and there are no account-maintenance, inactivity, or market-data fees. The per-contract trading fee is the entire cost structure for retail traders. Some third-party payment methods that Kalshi does not directly support may have their own fees, but Kalshi itself charges nothing on the money-movement side.

Do fees get charged twice — once to buy and once to sell?

Yes. The formula applies on both sides of a round trip because every trade is a separate fill against the order book. If you buy 100 contracts at $0.50 and later sell them at $0.55, you pay the fee on the buy and again on the sell. Factor the double charge into any breakeven or risk-reward calculation before entering a position.

Are there fee discounts for high-volume traders?

Kalshi's public retail fee schedule does not currently include a volume-tier discount, though institutional market-maker programs have separately negotiated schedules. If you trade meaningful size and want to explore market-maker status, contact Kalshi directly. For the vast majority of retail traders, the standard 7¢ × p × (1 − p) formula is the fee you will pay.

Are Kalshi fees the same across every contract?

The core formula is the same, but Kalshi periodically runs promotional fee waivers on newly listed contract categories to seed liquidity. During a promotional window a category can be zero-fee or heavily discounted. Always check the market details page before assuming — the fee shown at order-preview time is the authoritative number.

What about the spread — is that a fee?

The bid-ask spread is not a fee that Kalshi charges; it is the natural gap between the best resting bid and the best resting ask on the order book. On liquid markets the spread is usually 1–2¢. On thin markets it can be much wider. When you cross the spread with a market order you effectively pay half of it in slippage, which is separate from and additive to the trading fee.

How can I model my breakeven edge with fees included?

Take the fee percentage (7 × price × (1 − price)), double it for round-trip, add half the spread as slippage, and double that for round-trip too. That total is the minimum edge in percentage terms you need on your entry probability estimate to break even. On a typical mid-book market with a tight spread, plan on needing roughly 3–5% of edge before fees turn into net profit.