Definition
Arbitrage (arb) locks a guaranteed profit by betting all outcomes of an event at different books where prices disagree. Requires the sum of implied probabilities across books to be below 100%. Profit = 1 − (sum of implied probabilities). Arbs are rare, small, and close fast as books sync prices. Requires accounts at multiple books, fast execution, and awareness that books will limit or close accounts identified as arbers. Best found in player props and game props where pricing is less efficient.
Worked Example
Book A: Team X +105 (implied 48.78%). Book B: Team Y +102 (implied 49.51%). Sum = 98.29%. Arb exists. To guarantee $100 profit on $2,000 total: stake on X = 2000 × (49.51 ÷ 98.29) = $1,007; stake on Y = 2000 × (48.78 ÷ 98.29) = $993. X wins: $1,007 × 1.05 = $1,057.35. Y wins: $993 × 1.02 = $1,012.86. Both cases > $2,000 staked. Profit ≈ $35.
Why It Matters
Arbing provides risk-free profit but risks account limitation. More useful as a line-shopping strategy — find the best price before the arb closes rather than trying to execute both sides simultaneously.