See Further
The same question, priced two ways.
Kalshi and Polymarket ask the same thing in different words, at different prices, and nobody puts them on one line. We do — then keep score on whether you were right.
Free tools, working today
The same math the terminal prices real positions with. No account.
What a Kalshi or Polymarket trade actually costs, entry and exit — using each venue’s real published schedule, including the categories Polymarket charges nothing on.
Open the fee calculatorTurn a contract price into American or decimal odds, then strip the vig out of a sportsbook line so the two are finally comparable.
Open the converterThe terminal opens shortly.
Both exchanges on one line with the gap between them printed, sportsbook lines beside the market, your whole book across both venues — and, eventually, the only question a prediction trader can’t answer alone: when you buy at 70¢, does it actually happen 70% of the time?
Why the calculators exist
Comparing an exchange price to a sportsbook line properly means converting the unit, removing the book’s vig, and subtracting what both venues charge to trade. Every one of those steps is where a real edge quietly disappears — and most tools skip at least one of them. So we made the steps public and free.
These calculators are informational and are not financial or trading advice. Fee schedules are modelled from each venue’s published rates and can change.