Kalshi Arbitrage Calculator
Compare a Kalshi contract with sportsbook odds or with Polymarket, using Kalshi's real fee formula. Size the trade by contracts or by budget, and see the profit on every outcome. New to this? Read the complete Kalshi arbitrage guide. For sportsbook-only arbs, use the arbitrage calculator.
Kalshi vs Sportsbook
Kalshi side
Sportsbook side (the other outcome)
Each contract pays $1 if its outcome happens. Check the fee multiplier of the series before you trade; Kalshi can change it.
| Leg | Price / odds | Cost | Pays if it wins |
|---|
| If this happens | Total paid | Total cost | Profit |
|---|
Kalshi vs Polymarket
Kalshi side
Polymarket side (the opposite answer)
Rates are for Polymarket's international platform (sports 0.05 since July 2026; makers pay nothing). Polymarket US, the separate CFTC-regulated app, has its own fee schedule; use a custom rate for it.
Both platforms must settle the question by the same rules (overtime, postponements, draws). If the rules differ, this is a bet, not an arbitrage.
| Leg | Price | Fee | Cost |
|---|
Kalshi Price to Odds
The per-contract fee here is unrounded. On a real order, Kalshi charges the fee on the whole fill and, for most accounts, rounds it up to the next cent.
| Before fee | After fee |
|---|
Kalshi fees used here
| Fee | Formula | Applies to |
|---|---|---|
| Taker (order fills right away) | roundup(0.07 × C × P × (1 − P)) | Almost all sports series |
| Taker, MLB | roundup(0.035 × C × P × (1 − P)) | Pro baseball series (multiplier 0.5) |
| Maker (resting order) | roundup(0.0175 × C × P × (1 − P)) | Series with maker fees, including major league games. Other series: no maker fee |
| Settlement, ACH deposit and withdrawal | $0 | All markets. Card deposits cost up to 2% |
C = number of contracts, P = price in dollars. For most accounts the fee on each fill ends up rounded up to the next cent; Kalshi tracks rounding across the fills of one order and can rebate the overpayment, and direct members are rounded to $0.0001 instead. So treat the results here as close estimates. Sources: Kalshi fee schedule (effective Feb 5, 2026), Kalshi fee rounding docs and Kalshi's public API series settings, checked October 12, 2026. Kalshi can change fees and multipliers, so confirm on the order screen before you trade. Full details: Kalshi fees explained.
How Kalshi arbitrage works
A contract price is a probability
A Kalshi contract pays $1 if its outcome happens. A price of 52¢ means the market gives that outcome about a 52% chance, which is the same as decimal odds of 1 / 0.52 = 1.92.
The fee changes the odds
Kalshi charges more when the price is near 50¢ and less near the extremes. Add the fee per contract to the price before you compare it with a sportsbook. At 52¢ and the standard rate, the fee is about 1.75¢, so the effective odds are 1 / 0.5375 = 1.86.
Example: Kalshi vs a sportsbook
A sportsbook offers 2.25 on Team A. Kalshi sells "Team B wins" at 52¢. Buy 200 Kalshi contracts for $104 plus a $3.50 fee, and bet $88.89 on Team A at the sportsbook. Either way you collect $200 on a total cost of $196.39, a profit of about $3.61 (1.8%).
Example: Kalshi vs Polymarket
YES on Kalshi at 45¢ plus a fee of about 1.73¢, and NO on Polymarket at 50¢. Polymarket takes its 0.05 sports fee in shares (2.5% of the shares at 50¢), so each share you keep costs about 51.28¢. Together a pair costs about 98.02¢ and pays $1, so you keep about 2¢ per pair after both fees.
Check before you trade
Both sides must be settled by the same rules: overtime, postponed games and draws. Check the depth of the order book, because the price shown may only be available for a few contracts. Your money is locked until the market settles unless you sell earlier.
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For educational purposes only. This is not financial advice. Results assume every order fills at the prices you entered. Prices move fast, and fees and multipliers can change, so confirm them on each platform before you trade. Trade only where it is legal for you, and only with money you can afford to lose.