Prediction Market Fee Calculator
See how much each platform charges at a given contract price.
Results
| Platform | Total Fees (100 contracts) |
|---|---|
| Kalshi (Taker) | $1.751 |
| Kalshi (Maker) | $0.438 |
| PredictIt | $5.000 |
| Polymarket | $1.000 |
| Opinion | $25.000(min fee) |
| ProphetX | $1.000(on profits) |
Polymarket fees vary by market category. Opinion has a $0.25 minimum fee per contract and requires a minimum $5 purchase. ProphetX charges 2% on profits only (no fee on losing trades). All fees shown are taker fees. Kalshi and Polymarket use a P×(1-P) curve; fees are highest at 50¢ and approach zero near extremes.
What does this calculator do?
This tool estimates the per-contract trading fees you should expect to pay on popular prediction markets and displays them side by side so you can make apples-to-apples comparisons. Prices on exchanges are quoted in dollars per $1 payoff — for example, 0.60 means you pay sixty cents now and receive $1 if the event resolves in your favor. Each platform layers on fees differently, and because those policies affect your true cost in different ways, a simple price comparison can be misleading.
Kalshi charges a transaction fee when you place orders — taker fees are higher than maker fees, and both scale with contract price. PredictIt charges a fee only when you win: 10% of net profit, which sounds modest but compounds significantly on winning positions. Polymarket currently charges nothing. The calculator normalizes all of this so you can quickly see the incremental cost per contract on each venue at a given price.
How should you use these numbers? If you're sizing a single directional bet, add the relevant fee to your entry price to understand your effective cost basis. If you are comparing two platforms, compare price + fee across venues rather than raw price alone. If you are building a cross-exchange hedge, remember that Kalshi's fee is paid at entry regardless of outcome, while PredictIt's fee reduces proceeds only in the scenario where that leg wins. Many edges look healthy in a spreadsheet but shrink after you incorporate platform specifics — this page helps you sanity-check that effect quickly before you commit capital.
We don't include account-level or withdrawal fees (e.g., PredictIt's 5% cash-out charge) because those depend on personal behavior. We also assume orders are filled at your stated price with sufficient liquidity. Slippage, partial fills, or cancellations can change your economics more than the fee itself. Use this alongside the Expected Value and No-Vig calculators when you want a fuller picture of whether a quote is truly attractive after frictions.