Fee and break-even calculator

Enter a price and size to see what a trade really costs, what it pays, and how likely the event has to be for it to make sense after fees.

Exchange and fee type

Price per contract (cents)

Contracts

—Fee

—Total cost

—Profit if it settles Yes

—Break-even probability

—American odds

—Decimal odds (after fees)

Fee formulas: Kalshi round-up(0.07 × C × P × (1−P)) to the cent; Polymarket US 0.0695 × C × P × (1−P); Polymarket.com category rates, rounded to 5 decimals. Rates as of November 2026 — see Kalshi fees and Polymarket fees. Estimates only; the exchange's own confirmation is final.

How the break-even number works

A contract pays $1 if the event happens. If your all-in cost per contract (price plus fee) is 41.7¢, the event needs to happen more than 41.7% of the time for the trade to pay off on average. Compare that number with your own estimate, not with the market price.