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 & Profit Calculator

Compare published fee layers for Kalshi, Gemini Predictions, and Polymarket, or work out what your own position cost. The position calculator combines separate fills into a weighted average and shows profit after your confirmed fees.

Calculate average entry price, payout & break-even → Compare fee schedules ↓

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.

Your fills → your position

Average entry price, profit & break-even calculator

Added to a Kalshi position in a separate order? Enter each executed fill to see the combined average price. Larger fills count more. Fees are separate inputs, so the result uses what you actually paid instead of guessing a schedule.

One market, one side, still held. All rows must be purchases of the same YES or NO outcome, with none of these contracts sold. This calculator does not match sold lots, combine YES and NO, net different markets, or handle partial/nonstandard settlements. It describes entry cost, not tax cost basis.

Use the total fee for each fill, not a per-contract fee. Zero must be entered explicitly; an empty fee is unknown. Up to 50 fills and 1,000,000 combined contracts. Quantities and dollar fees accept 6 decimal places; prices accept 4 decimal places in cents.

Compare a sale of the entire position

This calculation runs locally in your browser. Fill and fee values are not sent by this calculator or saved between visits.

Why adding to a position changes the average price

In this synthetic example, 10 contracts at 40¢ cost $4 and 20 at 60¢ cost $12. The combined entry price is $16 ÷ 30 = approximately 53.3333¢, not the simple 50¢ average of the two prices. If the confirmed fees were $0.10 and $0.20, total entry cost would be $16.30. A standard winning payout of $30 would leave $13.70 profit, while a loss would cost $16.30. Those fee amounts illustrate inputs; they are not a current fee quote.

The formulas behind the result

Weighted average entry: sum of (contracts × execution price in dollars) ÷ total contracts.
All-in cost per contract: (purchase cost + confirmed entry fees) ÷ total contracts.
Standard settlement profit: winning payout − total entry cost. A losing side pays $0, leaving the entry cost as the loss.
Break-even probability: total entry cost ÷ full winning payout. This cost threshold does not predict the event.
Full-exit profit: (contracts × exit price) − exit fee − total entry cost.

Position calculator added September 16, 2026. Its arithmetic uses only your entries and does not refresh or override the dated fee comparison above. See Kalshi's fee explanation, execution and partial-fill guidance, and settlement details for the assumptions to verify.

For the next decision, read how probability estimates affect position sizing or why trade-level and account-level P&L can differ. A supported bot rule can enforce the price, quantity and risk limits you choose; this calculator does not place orders.

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 →

To test a hypothetical fill against your own probability estimate and loss cap, use the Polymarket paper strategy planner.

Considering Robinhood automation? The Robinhood compatibility checker separates documented stock, option, and crypto agent tools from the event-contract gap. This calculator does not quote Robinhood fees.

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.