Tools › Kalshi Kelly calculator
Fee formula from Kalshi's fee schedule effective July 7, 2026 · 2,000 simulated runs with a fixed seed · runs in your browser
With a $1,000 bankroll, a 40¢ contract you think wins 50% of the time, and 100 contracts bought as a taker, the fee lifts the cost to 41.68¢ a contract, and full Kelly stakes 14.27% ($142.66). Half Kelly is $71.33 and quarter Kelly $35.67. Over 100 similar bets, full Kelly fell to half the bankroll in 39.0% of 2,000 simulated runs, half Kelly in 8.1% and quarter Kelly in 0.2%.
Cost with the taker fee: 41.68¢
Full Kelly: $142.66
Half Kelly: $71.33
Quarter Kelly: $35.67
Fell to half the bankroll: full 39.0% · half 8.1% · quarter 0.2%
The simulation stakes the same share of the current bankroll on each bet and assumes your probability is right.
A contract that costs k (price plus the taker fee per contract) and pays $1 wins 1 - k per dollar of cost with your probability q and loses its cost otherwise. The Kelly share of the bankroll is (q - k) / (1 - k). Staking twice that much drives long-run growth to about zero, and a probability that is a little too high turns full Kelly into overbetting, which is why fractions of Kelly are common. Taker fees are rounded up per order, so small orders pay more per contract.
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It is the share of your bankroll that maximizes long-run growth when your probability is right: (q - k) / (1 - k), where q is your probability and k is what a contract costs you including the fee. If k is at or above q there is no edge and Kelly says not to bet.
The taker fee raises the cost per contract: 100 contracts at 40¢ cost 41.68¢ each, so a 50% view has an edge of 8.32 points instead of 10. Small edges can disappear entirely.
Many traders use half or quarter Kelly: for small edges half Kelly keeps about three quarters of the long-run growth with much smaller drawdowns, which also protects you when your probability is too optimistic. The simulation shows how often each size falls to half the bankroll.
No. It is arithmetic on the numbers you enter; the probability and the decision are yours.