Arbitrage Calculator

How the arbitrage calculator works

An arbitrage exists when you can cover every outcome and still come out ahead. Convert each price to an implied probability and add them up. If the total is under 100%, there's free money on the table — you just need to size each stake correctly.

• Arb % = (1 ÷ odds A) + (1 ÷ odds B). Under 100% = arb.
• Stake on A = total × (1 ÷ odds A) ÷ arb %
• Profit = guaranteed return − total staked

Worked example

YES trades at 2.10 on one platform and the other side at 2.10 on another. The market totals 1/2.10 + 1/2.10 = 95.2% — an arb. Stake $1,000 split ~$500/$500 and you collect ~$1,050 either way: about $50 (5%) risk-free, before fees.

Finding arbs on Polymarket

Cross-platform gaps (Polymarket vs Kalshi) and even within a single market's YES/NO spread are where arbs appear. They vanish fast, so most traders use a scanner — see the arbitrage tools in the directory and our Polymarket–Kalshi arbitrage guide. Convert formats first with the odds converter.