Prediction Markets / Trading fees
Polymarket & Kalshi Fee Calculator
Select a venue and market type, then inspect the fee and settlement-independent trade value. The fee curve changes with contract price.
Your inputs
Manual model only. Check current market rules, fee schedule, liquidity and settlement terms.
How to use this calculator: Trading fees
Select a venue and market type, then inspect the fee and settlement-independent trade value. The fee curve changes with contract price.
Worked example: At $0.50, the maximum price-curve factor p × (1−p) is 0.25. An illustrative 7% curve produces $1.75 on 100 contracts.
Important limitation
Venue schedules, maker rules, rebate programmes, unit rounding, fees in shares, and category eligibility change.
Manual model only. Check current market rules, fee schedule, liquidity and settlement terms.
Cash fee versus shares received
Keep the contracts bought separate from the cash commission. The published Polymarket formula describes taker fees in USDC; this calculator does not remove shares to invent a share-based fee.
Use this only after identifying the venue and market category. A fee estimate is meaningful when the schedule and role are known; otherwise treat the output as a sensitivity check, not a live quote.
A fee can eliminate a small spread. Enter both legs in YES/NO arbitrage to see the difference.
Check the market-specific schedule
Kalshi may charge maker fees on selected series, while certain taker series use a different coefficient. Choose a custom fee model only after verifying the applicable fee table.
Related calculations
FAQ
Why does the fee peak around 50 cents?
The p × (1−p) factor is highest at 0.50. The applicable rate and rounding still depend on the market and trading venue.
Does every Kalshi limit order avoid a fee?
No. Some resting-maker orders are charged maker fees. Check the fee schedule for that series and select whether a maker fee applies.
Does Polymarket always subtract shares from my purchase?
The current official taker-fee specification describes a fee denominated in USDC. This calculator keeps the purchased shares and cash fee separate.
Important limitation
Venue schedules, maker rules, rebate programmes, unit rounding, fees in shares, and category eligibility change.
Polymarket current fee specification · Kalshi official fee schedule