Arbitrage

Placing offsetting bets across multiple venues to guarantee profit regardless of outcome. Rare and short-lived in mature markets; modest in size when found.

An arbitrage opportunity exists when the prices across multiple venues for opposite sides of a market sum to less than 100% (the implied probabilities under-count, meaning whoever wins, you've collected enough on your two bets to net positive).

Formula: An arb exists when (1/A) + (1/B) < 1, where A and B are decimal odds for opposite sides.

Example: Lakers +110 (decimal 2.10) at DraftKings, Celtics -100 (decimal 2.00) at FanDuel. 1/2.10 + 1/2.00 = 0.476 + 0.500 = 0.976. Less than 1, so an arbitrage exists. Bet $476 on Lakers + $500 on Celtics; whichever wins, you collect $1000 (vs $976 total wagered) for a 2.4% locked profit.

Arbs are rare and require: - Accounts at multiple sportsbooks - Fast execution (lines move in seconds) - Modest stakes (books limit arb hunters quickly)

Cross-venue arbs between Kalshi and sportsbooks are more common because the two markets aren't tightly linked yet. As Kalshi matures, these will compress.

SportsBookISH doesn't actively recommend arbitrage but the edge tables surface big book/Kalshi disparities that are arb candidates.

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