Glossary

What is arbitrage in sports betting?

Last updated 2026-07-04

Sports betting arbitrage is backing every outcome of an event at different sportsbooks whose combined implied probability is under 100%, guaranteeing profit whichever side wins. Real cross-book arbs run 0.5% to 3% and exist because books reprice at different speeds.

The detection math is one line: sum 1/decimal odds across the best price on each outcome; under 1.0 is an arb, and the margin is 1/total minus 1. Stakes are split proportionally to each outcome's implied probability so every result returns the same amount.

The execution reality is harsher than the math: lines move between your first and second bet, books limit stake sizes, and accounts that consistently take stale prices get restricted. Speed and book selection matter more than margin size; a 10% "arb" is almost always a stale line or a bet that will be voided.

Split stakes with the arbitrage calculator, and read the arbitrage detection guide for the scanning architecture. One multi-book call per sport replaces scraping fifty sites.

Compute it with the API

curl "https://api.theoddsapi.com/intelligence/arbitrage?sport_key=basketball_nba" \
  -H "x-api-key: YOUR_API_KEY"

Precomputed cross-book arbitrage opportunities, flagged when the margin is suspiciously large. Business tier. Free key in minutes.

Related terms: Middling · Line Shopping · Expected Value (+EV) · Betting Limits · Full glossary