YES + NO Sum
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Arbitrage?
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Gross Spread
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Gross Profit
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Net Profit (after fees)
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When Should You Use This?
Use this calculator to check if a Polymarket market has a Dutch-book arbitrage opportunity. If the sum of YES and NO prices is less than $1.00, you can buy both sides and guarantee a profit regardless of the outcome.
How It Works
1
Enter Prices
Input the current YES and NO ask prices from the Polymarket order book. These are the prices you would pay to buy each side right now.
2
Check the Sum
If YES + NO < 100 cents, arbitrage exists. The calculator shows the exact spread and whether fees eat the profit.
3
Size Your Trade
Enter how much capital you want to deploy. The calculator shows how many pairs you can buy and your net profit after fees.
Frequently Asked Questions
Dutch-book arbitrage means buying a complete set of outcomes (YES + NO) for less than the guaranteed payout ($1.00). Since one side must win, you are guaranteed to receive $1.00 per pair, locking in a risk-free profit.
In 2026, simple arbitrage opportunities are rare and last only 2-7 seconds on average. Automated bots capture 73% of arbitrage profits. Retail traders can still find opportunities in less liquid markets.
Often yes. With Polymarket's ~1.5% taker fee on resolution payouts, the YES + NO sum needs to be below about 98.5 cents for a profitable arbitrage after fees.
Yes. You can buy YES on Polymarket and the equivalent NO on Kalshi (or vice versa) if prices disagree enough to cover fees on both platforms.
For markets with 3+ outcomes (like 'Who will win the election?'), if the sum of all outcome prices is less than $1.00, you can buy all of them for a guaranteed profit.