Who gets paid when you bet?

Works for any YES/NO contract on Polymarket, Kalshi or any other prediction market. Enter the two prices for the side you want to buy and your stake. See what the spread costs you before anything happens.

Where to find the prices: open the market's order book. The lowest ask is your buy price. The highest bid is your sell price.

¢
¢
$

Fee per trade = rate × shares × price × (1 − price). Charged when you buy and again when you sell, if you take the price shown in the book.

The sell price must be lower than the buy price.

Cash out one second after you buy and you get back
$87.50
Total lost if you cash out right away$12.50
  of that, to the spread$12.50
  of that, platform fees (in + out)$0.00
Fee to get in$0.00
Shares you get625
Sell price you need to break even16.0¢
Payout if your side wins (held to the end)$625.00
Implied odds you are paying for16%
* Fee rates by platform and category (taker, Nov 2026)
Polymarket: Crypto7%
Polymarket: Sports, Economics, Culture, Weather, Other5%
Polymarket: Finance, Politics, Tech, Mentions4%
Polymarket: Geopolitics0%
Kalshi: most markets7%
Kalshi: some series0%

The rate is not what you pay. Your fee as a share of your bet = rate × (1 − price). So a 4% rate costs 3.4% of your bet at 16¢, 2% at 50¢ and 0.2% at 95¢. Cheap contracts pay the most. If you post your own order and wait (maker), Polymarket charges nothing. Sources: Polymarket fees, Kalshi fee schedule.

Assumes your whole bet fills at the best price. Big bets usually climb the order book and pay more. Fee rates from the official Polymarket fees page and Kalshi fee schedule (checked Nov 2026); exact rounding may differ by a cent. This is a math tool, not financial advice.

Made by @0ddscent. We score AI models against prediction markets: see the track record.