Which prediction market has the lowest fees?

There is no durable platform-wide winner. The answer depends on the exact series or category, maker/taker role, executable price, builder fee, program eligibility, rounding, spread, depth and likely exit.

Does the calculator include spread and slippage?

No. It compares published transaction-fee layers. Spread, slippage, funding, transfer and exit cost require separate market and account inputs.

Why can a rebate be unknown?

A program may depend on category, listing date, price band, wallet architecture, rolling volume, a daily pool or other traders. Unknown inputs remain unknown rather than being treated as zero or guaranteed revenue.

Prediction Market Fee Calculator

Compare the current published fee layers for Kalshi, Gemini Predictions, and Polymarket. The calculator keeps platform fees, temporary rebates, and Polymarket builder charges separate—and leaves missing costs unknown.

Sources reviewed July 23, 2026. Similar formulas do not make contracts interchangeable. Confirm the contract rules, benchmark, executable order-book price, and current schedule before acting.

Compare one hypothetical fill

Contracts or shares Execution price (¢) Liquidity role Kalshi multiplier Polymarket category Polymarket builder fee (bps) Polymarket 30-day weighted volume

I confirmed this Gemini maker fill is eligible for the current rebate program. I confirmed the Polymarket account path is eligible and is not a third-party omnibus-wallet integration.

How to read the comparison

Platform fee is the current published transaction fee under the assumptions selected. Builder fee is an additive Polymarket application charge. Confirmed rebate is deducted only when the documented inputs are explicitly confirmed. The known total is not a forecast of complete execution cost.

Kalshi's general schedule currently defaults to a taker multiplier of 1 and maker multiplier of 0, but listed series can override either. Gemini rounds base fees up to the next cent; its observed maker rebate rounds down. Polymarket uses category and market configuration, five-decimal platform fees, and separate maker/taker incentive programs.

Primary sources

Need the deeper Polymarket view?

Our Polymarket fee guide separates the US schedule from the category-based CLOB V2 platform fees, builder charges, and incentive mechanics without inventing a guaranteed payout.

Open the live Polymarket fee guide →

Build with explicit cost controls after you verify which published fee schedule applies to your market.

Method: our public research and revision policy. Educational research only; not financial, legal, tax, or eligibility advice.