Arbitrage Betting: How to Find and Lock In Guaranteed Profits

Arbitrage betting lets you guarantee a profit by placing bets on every outcome of an event at different sportsbooks — when the combined odds create a gap in the market. This guide shows you exactly how it works and how to calculate your stake for each leg.

What Is Arbitrage Betting?#

An arbitrage (or "arb") exists when two or more sportsbooks price the same event differently enough that betting on all outcomes still yields a guaranteed profit.

The key insight: sportsbooks set odds independently. When their prices diverge, the combined implied probability can drop below 100% — leaving a gap you can exploit.

Example:

| Sportsbook | Outcome | Odds (American) | Decimal | |---|---|---|---| | Book A | Team A wins | -110 | 1.909 | | Book B | Team B wins | +120 | 2.200 |

Implied probabilities: 52.38% + 45.45% = 97.83%

Because 97.83% < 100%, this is an arbitrage opportunity. Profit = 100% − 97.83% = 2.17% of your total stake, guaranteed.

How to Calculate the Arb Percentage#

The arb percentage tells you whether an opportunity exists and how profitable it is.

Step 1: Convert to Decimal Odds#

If odds are in American format:

• Positive (+120): decimal = (120/100) + 1 = 2.200
• Negative (-110): decimal = (100/110) + 1 = 1.909

Step 2: Calculate Implied Probability Per Leg#

For each leg: implied probability = 1 / decimal odds

• Leg A: 1 / 1.909 = 0.5238 (52.38%)
• Leg B: 1 / 2.200 = 0.4545 (45.45%)

Step 3: Sum the Implied Probabilities#

52.38% + 45.45% = 97.83%

A sum below 100% = arb opportunity. A sum above 100% = no opportunity (the house has an edge).

Step 4: Calculate Guaranteed Profit and ROI#

With a $100 total stake on a 97.83% arb:

• Guaranteed profit = $100 × (1 − 0.9783) = $2.17
• ROI = 2.17%

How to Stake Each Leg#

Distributing your total stake correctly ensures you profit regardless of which outcome wins.

Formula:

Stake_i = Total Stake × (1 / d_i) / arb_sum

Where arb_sum = sum of (1 / d_i) for all legs.

Continuing the example with $100 total:

| Leg | Decimal | 1/d | Stake | |---|---|---|---| | A (Book A) | 1.909 | 0.5238 | $100 × 0.5238 / 0.9783 = $53.54 | | B (Book B) | 2.200 | 0.4545 | $100 × 0.4545 / 0.9783 = $46.46 |

Check: if A wins → $53.54 × 1.909 = $102.21; if B wins → $46.46 × 2.200 = $102.21. Profit either way: $2.21 (rounding-adjusted).

Use the Arbitrage Calculator — enter the odds and total stake, and it calculates exact leg amounts instantly.

How to Use the Arbitrage Calculator#

1. Enter odds for Leg A from the first sportsbook (any format: American, decimal, fractional).
2. Enter odds for Leg B from a different sportsbook.
3. Check the Arb % — if it's below 100%, you have an opportunity.
4. Enter your total stake — the calculator shows the exact amount to place on each leg.
5. Add more legs for three-way markets or multi-book spreads.

Risks and Limits of Arbitrage Betting#

Arbitrage is theoretically risk-free, but real-world execution carries these challenges:

• Account restrictions. Sportsbooks monitor for arb patterns and may limit stakes or close accounts.
• Odds movement. Odds change fast. By the time you place both bets, one line may have moved unfavorably.
• Maximum bet limits. Books often cap stakes on sharp action, preventing you from achieving your calculated stake sizes.
• Withdrawal delays. Arbitrage requires capital spread across multiple books simultaneously.
• Rounding and fees. Small arb margins can be wiped out by rounding errors or withdrawal fees.

Use arb betting as part of a diversified betting strategy, not as a standalone income source.

Related Tools#

• No-Vig Calculator — find the fair price of any bet
• +EV Calculator — estimate expected value from your edge
• Single Bet Calculator — calculate payout and implied probability