free tool
arbitrage calculator.
Enter the YES price on each exchange. The calculator finds the opposite-side arb (YES on the cheaper venue, NO on the dearer one), and shows whether the spread survives fees + slippage. No signup.
The play: buy YES on Kalshi at 48.0¢ + buy NO on Polymarket at 47.0¢. One side settles $1.
cost to lock $195.0¢
gross edge+5.0¢
net edge (after buffer)+3.0¢
profit on $1,000+$32
✓ Locked-in arb: 3.16% return on capital, regardless of outcome.
The buffer is yours to set because real costs vary: Kalshi charges a trading fee, Polymarket adds USDC gas, and thin books mean slippage at size. For the exact fee math with a worked example, read the math, or see where the two exchanges disagree right now on live price gaps.