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. Kalshi charges a transaction fee when you place orders; PredictIt charges a fee only when you win; and Polymarket currently charges no trading fee. Because those policies affect your true cost in different ways, a simple price comparison can be misleading. This calculator normalizes the fee piece so you can quickly see the incremental cost per contract on each venue at a given price.

Enter a contract price in the field above and hit Calculate. We compute Kalshi’s taker and maker fees using the official formulas and then round up to the nearest cent on the total order before converting to a per‑contract amount, which mirrors how execution fees accrue in practice. For PredictIt, we estimate the 10% fee on profits as a per‑contract figure – e.g., at 0.60 the unrealized profit is 0.40, so the fee is 0.04 when the contract wins. We show 0 for Polymarket, which reflects their current fee schedule for buys and sells. The outputs are intentionally formatted as currency so you can mentally add them to quoted prices or subtract them from potential proceeds when you’re evaluating trades or building arbitrage baskets.

How should you use these numbers? If you are 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.

A few caveats: 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. Finally, this page is not legal, financial, or trading advice – it’s a simple estimator designed to keep fee math from tripping you up so you can focus on finding good markets. Use it alongside our Expected Value and No‑Vig tools when you want a fuller picture of whether a quote is truly attractive after frictions.