Tools
Free, and nothing to sign up for
Four tools. No account, no email address, no paywall.
Every rate a calculator uses is traced to the venue's own published schedule and stamped with the date it was read. Where a coefficient is our working assumption rather than a published figure, the tool says so on the page instead of quietly using it.
Scanner
Cross-venue scanner
Live candidate feed. Both taker legs priced from each venue's published schedule, republished every 60 seconds, with the size ceiling on every row.
Calculator
Kalshi Fee Calculator: the curve, the maker rate and the rounding
Kalshi takers pay 0.07 x C x P x (1-P), rounded up to the next cent. Break-even at every price, plus what the rounding costs on longshots.
Calculator
Polymarket Fee Calculator ยท Break-even by price
Break-even is rate x (1 - price) of your stake: 2.00% at 50 cents, 3.60% at 10 cents on a 4% market. Every rate sourced and dated.
Reference
A prediction markets glossary
Every term used on this site, defined once, in the language traders use rather than the language marketing uses.
If you have never traded one of these markets, start with a fee calculator, then open the scanner to see what a spread looks like once that arithmetic is applied to both legs.