Methodology
- Convert each available outcome price to implied probability.
- Sum implied probabilities; if the total is below 1.00, an arbitrage exists.
- Size each side as stake_i = total_stake * implied_i / sum_implied to aim for equal profit on every outcome at the prices shown.
- Subtract execution risks: limits, palpable error voids, fee margins, and account limitations.
Where arbitrage actually shows up
Most cross-book arbs are small, short-lived, and concentrated in soft markets such as low-liquidity props, alt lines, and live odds. The advertised edge disappears once you account for stake limits and slow lines on one book.
- Three-way soccer arbs need all three prices to be live at the same moment
- Two-way prop arbs vanish when one book lowers its limit
- Boosted prices can create temporary arbs against unboosted books
- Stake caps mean partial fills can leave you exposed on the slower leg
Execution risk is the real cost
Sportsbooks limit, void, or restrict accounts that systematically take soft prices. The expected profit on a pure arb is the margin at the quoted prices minus the long-run cost of voids and stake reduction.
- Lead with the smaller, harder-to-cancel side first when prices move fast
- Treat palpable error voids as a real cost, not a rare event
- Avoid wash trades that draw bonus clawback reviews
- Track every leg and settlement so you can audit true realized edge
Two-way arbitrage example · Hypothetical example
Side A at +110 on Book 1 and Side B at +105 on Book 2.
| Field | Value | Effect |
|---|---|---|
| Side A implied | 47.62% | Decimal 2.10 |
| Side B implied | 48.78% | Decimal 2.05 |
| Sum of implied | 96.40% | 3.60 percentage points below 100% |
| $1000 stake split (A / B) | $493.98 / $506.02 | About $37.35 net before costs if both bets stand; stakes rounded to cents |
An arb that survives one book reducing limits to $50 was never really there.
Responsible-use note
Analytics should support disciplined decision-making, not guaranteed outcomes. Bet only where legal, never risk money you cannot afford to lose, and use limits before volume increases.
FAQ
Is arbitrage really risk-free?
No. The math can show a profit on every outcome at the prices shown, but execution carries risk. Voids, stake limits, palpable error rules, and slow lines on one side all turn an arb into an open position.
How big are typical arbs in liquid US markets?
Liquid spread and total markets clear within a few seconds. Realistic edges come from props, alt lines, low-liquidity sports, and boosts versus unboosted books.
Will arbing get my account limited?
Yes. Sportsbooks track winning, fast, and pattern accounts. Many arbers rotate books, vary stake sizes, and balance with some recreational volume to extend account life.
