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, Polymarket, or Polymarket US 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 converterOpposite sides on two venues: the stake split, the guaranteed payout and the profit after both venues’ fees. Kalshi, Polymarket, Polymarket US or a sportsbook.
Open the arbitrage calculatorBoth sides of a sportsbook line in, the fair probability and the book’s vig out. Refuses an incomplete book.
Open the no-vig calculatorThe taker fee on any Kalshi trade, by price, from the published schedule.
Open the Kalshi calculatorPolymarket and Polymarket US are separate exchanges with separate schedules. Both here.
Open the Polymarket calculatorFees, settlement and price grids side by side.
Open the comparisonThe win rate a trade needs after fees, buying the ask or resting a limit order, on all three exchanges.
Open the break-even calculatorWhat a price means, Polymarket US vs Polymarket, limit orders, and what happens when a game is postponed.
Read the guidesEvery Senate, governor and chamber-control race Kalshi and Polymarket both price, side by side.
See the racesThe terminal is open.
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 modeled from each venue’s published rates and can change.