A Kalshi contract priced at 62 cents pays a dollar if it resolves yes, which makes the price itself a stated probability: 62%. Comparing that number to a sportsbook line takes conversion, and Kalshi’s taker fee changes the effective price before that comparison is fair.
This calculator turns a contract price in cents into implied probability, decimal odds, and American odds, and runs the exchange fee for Kalshi or Robinhood into the result. It also works in reverse, turning a posted American odds line into the contract price a prediction market would need to match it.
Enter the contract price in cents first, the number a Kalshi, Polymarket, or Robinhood market shows for the side being priced. Pick the exchange next: Kalshi, Polymarket, Robinhood, or No fee, since the fee schedule changes what the price actually costs. Skip the price field entirely and enter American odds instead if the direction runs the other way, from a sportsbook line back to a contract price.
The result shows implied probability, American odds, and decimal odds straight from the price. Below that sits the profit per one dollar contract if it wins, the fee charged per contract on the chosen exchange, and the American odds after that fee is folded into the price.
Implied probability is just the price divided by 100, so a contract at 62 cents implies a 62.0% chance. Decimal odds come from 100 divided by the price, and American odds follow from that same probability: negative for anything priced above 50 cents, positive below it.
A 62 cent contract on Kalshi implies 62.0%, decimal odds of 1.613, and American odds of -163. Kalshi charges a taker fee of 7% of the expected profit per contract, calculated as 0.07 times price times 1 minus price, rounded up to the cent. On a 62 cent contract that profit is $0.38 per dollar if it wins, and the fee works out to $0.02 per contract. Added to the price, that fee turns -163 into -178, the number to compare against a sportsbook line.
This matters most when the same event is priced on a prediction market and a sportsbook, an election, a rate decision, an award, or any market both sides list. Comparing 62 cents on Kalshi to a -150 line elsewhere only works once the fee is folded in, since the raw conversion understates what the contract actually costs to buy.
The common mistake is quoting the fee-free implied probability as if it were the tradeable price. A 62 cent Kalshi contract is not a true -163 bet, it is closer to -178 once the fee is added, and that gap can be the difference between a real edge and a bet that only looked like one. A sharp bettor runs the fee into the price before comparing it to a sportsbook line, then bets whichever side offers the better number.
Does Polymarket charge a trading fee the same way Kalshi does? Most Polymarket markets carry no trading fee, so a contract price there converts to American odds and decimal odds directly, without an added cost layered on top the way Kalshi’s taker fee works.
How much does Robinhood’s fee change the price? Robinhood charges one cent per contract, a flat amount rather than a percentage of expected profit, so its effect on the American odds is smaller and more predictable than Kalshi’s fee, which scales with how close the price sits to 50 cents.
Why does the fee shrink as a contract price moves toward the extremes? Kalshi’s fee is 7% of price times 1 minus price, and that product is largest at 50 cents and smallest near 0 or 100 cents, so a contract priced at 95 cents carries a much smaller fee than one priced at 50 cents.
Can this run backward from American odds to a contract price? Yes, entering American odds in place of a contract price converts a sportsbook line into the cents price a prediction market contract would need to carry to match it, before any fee is added.