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Prediction market fees, worked out.

By Rocco Stoney · Updated November 3, 2026 · 6 min read

The formula both platforms share

Kalshi and Polymarket publish different fee schedules, but the core taker fee has the same shape:

fee = rate × contracts × p × (1 − p)

Here p is the contract price in dollars (0.63 for 63 cents) and rate is a platform- and category-specific number. The term p × (1 − p) is the variance of a $1 binary contract. It is 0.25 at 50 cents and falls toward zero near 0 or 100 cents, so fees peak on coin-flip contracts and shrink on near-certain ones.

Rates and exceptions change, so always confirm against the current source: Kalshi’s fee schedule and Polymarket’s fee documentation. The numbers below were checked on November 3, 2026.

Kalshi fees by price

Kalshi’s general taker rate has been 0.07, with the fee rounded up to the next cent per order. Some markets, often major events, use different rates, and some markets also charge makers. Allium’s September 2026 analysis walks through the same schedule.

The dollar fee is symmetric around 50 cents, but the fee as a share of your stake is not. Cheap contracts carry the heaviest percentage cost: a 10-cent contract pays 6.3% of its stake in fees on entry.

Polymarket fees by category

Polymarket’s documentation lists category rates and states that makers are never charged; takers pay, and makers receive a share as a rebate. Geopolitics markets were fee-free when checked. Representative taker rates: crypto 0.07; sports, economics, culture and weather 0.05; politics, finance and tech 0.04. Fees are calculated in USDC to five decimal places.

Polymarket availability, account type and fee schedule can differ between its international and US products. Check which one applies to you.

Fees move your break-even probability

This is the number that matters. For a contract that pays $1, your break-even win rate after fees is:

break-even = price + fee per contract

At 50 cents on Kalshi, the fee is 1.75 cents a contract, so you need the event to happen more than 51.75% of the time. If your model says 52%, your edge before fees looks like 2 points and is really a quarter of a point. Add a one-cent spread on entry and it is gone.

Selling before settlement is another trade, and it can carry another fee. A strategy that trades in and out pays the curve twice.

Small orders pay more on Kalshi

Rounding up to the cent is a fixed tax on small orders:

A bot placing many one-contract orders pays about 14% more in fees per contract than the same exposure in one order at this price.

What the fee formula means for strategy

• Coin-flip markets need the biggest edge. A 2-point disagreement at 50 cents rarely survives costs; the same disagreement at 90 cents might.
• Longshots are expensive in percentage terms. Buying 5-cent contracts loses a large share of stake to fees even when the dollar fee looks tiny.
• Making beats taking where makers are not charged. Resting limit orders can avoid taker fees, at the cost of not always getting filled.
• Cross-platform trades pay twice. See how this erases most Kalshi–Polymarket arbitrage.

Model fees before you trade

Use the odds calculator to convert prices and payouts, then add the per-contract fee from the current schedule. In Kelix Lab, strategy backtests include costs so a paper edge that only exists before fees is visible as what it is.

Educational content, not financial, legal or tax advice. Prediction markets involve risk, including loss of capital. Examples are illustrative calculations, not live quotes or trading results. Kelix is independent of Kalshi, Polymarket, Robinhood and sportsbooks.