Live scanner comparing prices across prediction markets and sportsbooks. Polymarket and Kalshi data is fetched in real time. Sportsbook odds are representative demo data — connect TheOddsPulse for live multi-book feeds.
Cross-Market Scanner
How Cross-Market Arb Works
This scanner compares prices for the same event across different platform types:
- Prediction markets (Polymarket, Kalshi) price events as binary contracts — you buy YES or NO shares at a price between $0.01 and $0.99
- Sportsbooks price events as odds — the implied probability is derived from the odds
When the cheapest YES across all platforms plus the cheapest NO across all platforms sums to less than 100%, an arbitrage exists. You buy YES on the cheaper platform and NO on the other, guaranteeing profit regardless of outcome.
Why Prices Diverge
Different platform types attract different participants. Sportsbook odds are set by professional oddsmakers and moved by sharp bettors. Prediction market prices are set by an open order book and moved by anyone — traders, political analysts, news junkies. These different information sources create pricing gaps, especially around:
- Breaking news — prediction markets may react faster to polls; sportsbooks may react faster to injury reports
- Low-liquidity events — thin prediction market books drift from fair value
- Cross-category events — events that are new to one platform type but established on another
Fee Impact
Polymarket charges ~2% on net winnings. Kalshi currently charges 0% on contract payouts. Sportsbook vig is embedded in the odds. A raw 3% arb might become a 1% arb after Polymarket fees — still profitable, but the margin matters.
Data Sources
| Source | Data | Status |
|---|---|---|
| Polymarket (Gamma API) | Binary contract prices, volume, market metadata | Live — fetched via proxy |
| Kalshi (REST API) | Binary contract prices, volume | Live — fetched via proxy |
| Sportsbooks | Multi-book odds, implied probabilities | Demo — representative data |
For live sportsbook data from 10+ books, connect TheOddsPulse to your arb pipeline.
See Also
- Cross-Market Arbitrage Guide — Deep dive into cross-market arb strategy
- Sports Betting Arbitrage Bot Guide — Build a full arb bot from scratch
- Arbitrage Calculator — Manual arb calculation with any odds
- Odds Converter — Convert between odds formats
- Polymarket API Guide — Full Polymarket API reference
- Kalshi API Guide — Full Kalshi API reference
This tool is maintained by AgentBets.ai. Found a bug? Let us know on Twitter.
Not financial advice. Built for builders.