Prediction market profit calculator, held to resolution

What it computes

One position, bought and held until the contract resolves, then withdrawn. Pick a venue, its fee schedule where it has more than one, whether your entry order took liquidity or rested, the price in cents, the number of contracts, which way the contract resolved and how you withdraw. You get each leg in dollars:

• what you put in — the contracts at your price, plus the fee on the fill, or minus it where a maker is paid;
• what is taken at settlement — a share of the gain on the two venues that charge there;
• what the withdrawal costs — a share of the amount moved or a flat charge per withdrawal, where the venue publishes one;
• what reaches your bank or wallet, the net, and the net as a share of what you put in;
• the break-even probability — the chance of winning at which this position comes out even after every cost above, which is what you put in divided by what a win leaves you with.

The last figure is the one no venue page gives you. A contract priced at 50 cents implies even odds before costs; after them, the position needs a better chance than that to be worth holding, and how much better depends on where the venue takes its cut. Below the result is the same position on all six venues, so a cost taken on the fill and a cost taken on the profit can be read in one column.

The default — 100 contracts bought at 50 cents as a taker, resolved in your favour, withdrawn by bank transfer — is the trade the fee calculator defaults to, carried through to the bank.

Where the numbers come from

Three legs, each from a document the venue publishes, each with its date or the day it was read, and all printed in this page's Markdown twin beside their documents.

• The fee on the fill is not restated here. It is read from the same table the fee calculator uses, so a schedule change moves both pages at once: Kalshi, Polymarket by category, Polymarket US and Gemini Predictions. PredictIt charges nothing on a fill, and ProphetX nothing on the fill of a straight trade.
• Settlement. PredictIt takes 10% of the profit on each share redeemed at a dollar, per its FAQ. ProphetX takes 2% of net gains per market at settlement, per its trading-fee page, version 1.2 of 1 October 2026. Kalshi's schedule sets no settlement fee on a yes-or-no contract, Gemini's says there are none, and Polymarket US pays a dollar a winning contract with a fee schedule that charges fills only.
• The withdrawal. PredictIt's FAQ, since its fee article was updated on 22 September 2026, charges nothing for a standard withdrawal from an active account; the 5% its terms keep for an inactive account is left out below. Gemini's transfer schedule makes ACH free and a USD wire $25. Kalshi's fee schedule makes ACH free, and Polymarket US documents every withdrawal method as free.

Where a document says nothing about a leg, the leg is not modelled rather than set to zero, and the figures it would have reduced are printed as "at most". Fees on the fill keep the venue's rounding; a share of profit is shown unrounded, because neither PredictIt nor ProphetX says how it rounds one.

What it leaves out

• The legs with no published rate. Polymarket states no charge for redeeming a winning share, and whether the redeem transaction costs gas depends on the wallet; its bridge then prices each withdrawal as a live quote, and the documentation's one worked example — a deposit, 10 USDC into pUSD — takes 10 dollars to 9.94. A crypto withdrawal from Kalshi pays its processor's fee and one from Gemini a network fee, both set at the time. Kalshi's fee schedule prices debit card deposits and says nothing of debit card withdrawals. ProphetX names no withdrawal fee at all, which is not the same claim as charging none.
• Venues whose withdrawal is not theirs to price. Robinhood, Webull, ForecastEx and Underdog Predict are reached through a brokerage, futures or linked fantasy account, which moves money on its own terms; Novig and PrizePicks Predict publish withdrawal articles that name no fee. Their fill fees are on the fee calculator.
• Charges that are not a rate on this position. Kalshi's reserved right to charge 0% to 2% on any rail, unused today; PredictIt's 3% on a credit-card deposit, and on an account with no login for twelve months its $2 a month and 5% of any withdrawal, principal included; Polymarket's on-ramp, which charges for the stablecoin before the first trade.
• Selling before resolution. This page holds to the end. Closing early pays a second fill fee at the exit price, and on PredictIt the profit fee falls on the sale instead.
• More than one position. ProphetX nets gains per market, so an offsetting position in the same market lowers the fee; PredictIt charges each profitable share and refunds nothing on a losing one; Gemini's wire fee is per withdrawal, so one withdrawal of several positions pays it once.
• Time. Money in a position until resolution, and in PredictIt's 30-day hold or Polymarket US's clearing period after it, earns nothing while it waits — see how money gets back out for putting a number on that.
• A contract that resolves neither way. A market settled at a last fair price, or under the alternative terms in its rules, pays something between nothing and a dollar; the outcome toggle has two positions.
• Rebates, credits and caps. Maker and taker rebate programmes paid later from a pool, promotional credit that cannot be withdrawn, and PredictIt's $3,500 limit on a contract, which caps the size this page will happily multiply.
• Tax. What reaches your bank is before any tax on the gain; who reports it, and on which form, differs by venue.