Prediction market fees: compare the cost of a complete trade

The useful comparison is the total cost of the same position. A percentage described as a trading fee may use a different base from another platform’s percentage. A broker can also charge a commission in addition to the exchange fee. Comparing the headline numbers without their formulas can reverse the apparent winner.

For this illustrative calculation, suppose you buy 100 contracts at $0.40 each. Each winning contract pays $1; each losing contract pays $0. The position costs $40 before fees. These are invented inputs for arithmetic, not quotes from any platform.

Assume Venue A charges $0.80 to enter and Venue B charges $0.30 to enter plus $1 to fund the account. If the funding transfer is made solely for this position, the total outlays are $40.80 and $41.30. A winning settlement produces $59.20 and $58.70 of profit respectively, assuming no other charge. A losing settlement loses the full outlay.

If the same $1 transfer supports ten equal positions, allocating one tenth to this position gives Venue B an attributable cost of $40.40. That changes the comparison. State how you allocate account-level costs instead of treating a transfer fee as either free or payable on every trade.

Now suppose both venues let you sell the 100 contracts at $0.55 before settlement. Gross proceeds are $55. If A charges another $0.80 to exit, net profit is $55 − $40 − $0.80 − $0.80 = $13.40. If B charges $0.30 to exit and you allocate the full $1 funding cost, net profit is $13.40 as well. The comparison for an early exit can differ from the comparison for holding.

Actual exit prices may differ between venues. If only half the order can sell at the displayed price, use the weighted average execution price for the whole order. A lower fee does not compensate for an unknown exit price. An unfilled limit order also cannot be counted as a completed trade.

Record the contract wording, side, quantity, entry price, order type, fee formula, rounding rule, planned exit and funding route. Add withdrawal costs where relevant. Separate charges you can establish from charges the documentation does not resolve.

Use the fee calculator to explore assumptions, then check the actual order preview. The Kalshi fee schedule and Robinhood event-contract overview illustrate why the current platform-specific formula matters. Sources checked 15 September 2026; the calculation above deliberately uses neither platform’s rate.