Kalshi trading fee

Also called Kalshi fee · taker fee

Kalshi's published per-contract trading fee, 0.07 x P x (1 - P), which peaks in the middle of the price range.

The formula is quadratic and symmetric around fifty cents, where it is largest. At 50¢ it is about 1.75¢ per contract; at 40¢ about 1.7¢; at 95¢ only about 0.3¢. Every calculation on this site that touches a Kalshi leg charges it — position sizing, hedge math, the cross-venue splitter, and each leg of a full-set scan.

Two consequences are worth internalising. The first is that the same trade can be worth taking on one venue and not the other. Near the middle of the range the Kalshi fee is roughly eight times the per-share cost booked against a Polymarket leg, so a thin edge that survives on Polymarket dies on Kalshi. Venue choice is part of the trade, not an afterthought.

The second is that the fee is heaviest exactly where cross-venue price gaps are most common. Disagreements cluster around even-money contracts, which is precisely where the fee peaks — so the one and two cent gaps that appear most often on any scanner are usually not worth capturing once both legs are charged. Check the venue's current published schedule before sizing on it; fee schedules change, and this entry describes the model this codebase implements today.

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Definitions describe how Polymarket and Kalshi behave and how WhaleTracks models them; venue rules and fee schedules can change, so confirm anything you size a position on with the venue itself. WhaleTracks is informational analytics, not financial advice. Past performance does not guarantee future results.