Cross-Market Arb Finder — Live Prediction Market Scanner
Live arbitrage scanner comparing Polymarket, Kalshi, and sportsbook odds. Real-time price gaps, arb percentages, and optimal stake splits.
Summary: Interactive cross-market arbitrage scanner that pulls live data from Polymarket and Kalshi APIs and compares against sportsbook odds (demo data). Displays real-time price gaps, arb percentages, fee-adjusted profit calculations, and optimal stake distributions for events priced across prediction markets and sportsbooks.
Topics: cross-market arbitrage, live arb scanning, Polymarket prices, Kalshi prices, sportsbook odds comparison, price gap detection, arb percentage calculation
Stack layers: Layer 4 — Intelligence
Related tools: Cross-Market Arb Finder, Polymarket CLOB API, Kalshi API, The Odds API
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 The Odds API for live multi-book feeds.
Cross-Market Scanner
Polymarket: loading...Kalshi: loading...Sportsbooks: demo data
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Sportsbook data shown is representative demo data. For real-time odds from 10+ sportsbooks, connect The Odds API.
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 variable taker fees by category — peak effective rates range from 0.75% (sports) to 1.80% (crypto) at 50% probability, with most categories between 1.00–1.56%. Geopolitics markets are fee-free. Kalshi charges a per-contract fee. Sportsbook vig is embedded in the odds. A raw 3% arb might become a 1% arb after platform 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 The Odds API to your arb pipeline.
Polymarket and Kalshi data is fetched in real time via API proxies. Sportsbook odds are currently representative demo data. You can connect The Odds API for live multi-book sportsbook feeds.
How does cross-market arbitrage work between prediction markets and sportsbooks?
When the cheapest YES price on one platform plus the cheapest NO price on another platform 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.
What markets does the arb finder scan?
The scanner covers politics, sports, and economics categories across Polymarket and Kalshi. It automatically identifies overlapping events between platforms and calculates arb percentages for each.
Does the scanner account for fees when calculating arb percentages?
Yes. The tool calculates fee-adjusted profit, factoring in Polymarket's variable taker fees (up to ~2% on general markets, higher on select crypto and sports markets) and Kalshi's per-contract fee. A raw 3% arb might become a 1% arb after fees.
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