Two-outcome arbitrage checker
Enter two yes-side implied probabilities for the same binary event across venues. The tool flags whether a proportional stake split can lock a positive return before fees.
Calculator
Only for compatible contract definitions. Fee/slippage buffer is added to the probability sum before the arb check.
What this tool does
Classic two-outcome arbitrage appears when the sum of implied yes probabilities across complementary quotes is below 1 (after converting odds to probability). This checker assumes you already verified the contracts share the same resolution rules.
Compatible definitions only
Do not compare Polymarket and Kalshi rows unless semantic compatibility is reviewed. Unlike strike prices, dates, or payout rules break the arithmetic. Insydr topic hubs keep incompatible pairs on separate rows for that reason.
Formula
Convert each quote to probability `p1`, `p2` for the same yes outcome (or yes vs no on a single binary). If `p1 + p2 < 1`, stakes proportional to the opposite side can lock a positive return before fees: stake1 ∝ p2, stake2 ∝ p1. If `p1 + p2 ≥ 1`, no classic arb exists on those quotes.
Limits
Ignores fees, latency, inventory limits, and settlement risk. Not advice. Always re-check observation times on the live market pages.