Free tool
Prediction market fee calculator
See exactly what Kalshi, Polymarket US, Gemini or Polymarket charges on an order, what the trade costs in total and what you keep if it wins. Free, no sign-up, and nothing you type leaves your browser.
Fee table
How prediction market fees work
All four venues use the same shape of formula: rate × contracts × price × (1 − price). The fee is largest at 50¢ and shrinks toward 1¢ and 99¢, because a contract near 50¢ has the most uncertainty. What differs is the rate, who pays it (takers, makers or both) and how the result is rounded.
- Kalshi: 0.07 for takers; 0.0175 for makers on series that charge makers. Rounded up.
- Polymarket US: 0.0695 for takers (0.10 on table tennis); makers pay nothing. Rounded to the cent, half to even.
- Gemini: 0.07 for takers; 0.0175 for makers, waived through December 31, 2026. Rounded up.
- Polymarket (international): 0.04 to 0.07 for takers depending on the category, none on geopolitics; makers pay nothing.
Rounding is per order, so small orders pay more per contract. No venue here charges a fee when a contract settles: a winning contract pays the full $1.
Comparing two venues side by side? See prediction market fees compared, or work out a full two-sided trade in the arbitrage calculator.
Fees decide whether a price gap pays. ArbTrader scans Kalshi, Polymarket US, Gemini and Polymarket for spreads that still pay after every venue’s fee, at the size actually for sale, and pings you when one opens.
Fee rules from each venue’s published schedule, checked October 31, 2026. Venues change fees; check the venue’s own fee page before trading. Not financial advice. ArbTrader isn’t affiliated with any venue named here.
Common questions
How are prediction market fees calculated?
Kalshi, Polymarket US, Gemini and Polymarket all charge rate times contracts times price times (1 minus price) on taker orders. The rate is 0.07 on Kalshi and Gemini, 0.0695 on Polymarket US and 0.04 to 0.07 by category on Polymarket.
Which prediction market has the lowest fees?
For takers, Polymarket US (0.0695) and Polymarket's politics, finance, tech and mentions markets (0.04) charge slightly less than Kalshi and Gemini (0.07). Makers pay nothing on Polymarket US and Polymarket, and nothing on Gemini through December 31, 2026.
Do I pay a fee when a contract settles?
No. On all four venues the trading fee is charged when the order fills. A winning contract pays the full $1.