EventArb
Free cross-platform arbitrage calculator for event contracts. Punch in YES/NO prices for the same event on Polymarket, Kalshi or Robinhood and it does the math each venue's fee schedule implies — whether buying opposite sides locks in a profit, what the spread nets after fees, and the opportunity cost of parking capital until resolution. Supports binary and multiple-choice markets, side-by-side venue comparison, shareable links and free email notifications when opportunities open.
Overview
Free cross-platform arbitrage calculator for event contracts. Punch in YES/NO prices for the same event on Polymarket, Kalshi or Robinhood and it does the math each venue's fee schedule implies — whether buying opposite sides locks in a profit, what the spread nets after fees, and the opportunity cost of parking capital until resolution. Supports binary and multiple-choice markets, side-by-side venue comparison, shareable links and free email notifications when opportunities open.
How it works
- Enter the same market's YES/NO prices as listed on each venue.
- It nets out each platform's fees and flags when buying opposite sides locks in more than they cost.
- Weighs the locked spread against the opportunity cost of capital for the contract's duration.
- A notification list emails you when cross-venue gaps open up.
Supported markets
- Polymarket
- Kalshi
- Robinhood
Completely free and donation-supported, including the email notification list for fresh opportunities.
Get EventArb- Fee-aware arbitrage math for Polymarket, Kalshi and Robinhood
- Binary and multiple-choice market modes
- Opportunity-cost model over the contract length
- Side-by-side comparison across venues
- Shareable calculation links
- Free email notifications when opportunities open
- Author
- Areeb & Sujay
- Category
- Arbitrage
- Website
- www.eventarb.com
- Added
- Aug 26, 2026
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