How to Calculate Arbitrage Percentages (With Examples)

Arbitrage betting works because sportsbooks sometimes disagree on odds enough to create a guaranteed profit margin. But how do you actually calculate whether an opportunity exists—and how much you stand to make?

In this guide, we'll walk through the exact math behind arbitrage percentages, with real examples you can follow along with.

What Is an Arbitrage Percentage?

The arbitrage percentage tells you whether a betting opportunity guarantees profit. Here's the simple rule:

• Under 100% = Arbitrage exists (guaranteed profit)
• Exactly 100% = Break even
• Over 100% = No arbitrage (the house wins)

The lower the percentage, the bigger your profit margin.

The Arbitrage Formula

To calculate the arbitrage percentage, you need to:

1. Convert each set of odds to implied probability
2. Add the implied probabilities together
3. If the total is under 100%, you have an arb

Converting American Odds to Implied Probability

For positive odds (+150, +200, etc.):

For negative odds (-150, -200, etc.):

Let's see this in action.

Example 1: Basic Two-Way Arbitrage

You find these odds on an NBA game:

• Sportsbook A: Lakers +150
• Sportsbook B: Celtics -130

First, convert to implied probability:

Since 96.5% is under 100%, this is an arbitrage opportunity with a 3.5% profit margin.

Example 2: No Arbitrage

Same game, different odds:

• Sportsbook A: Lakers +140
• Sportsbook B: Celtics -150

Over 100% means no arbitrage. That extra 1.7% is the sportsbook's built-in margin (the vig). This is why line shopping is so important—finding the best odds can turn a losing situation into a winning one.

Calculating Your Stakes

Once you've confirmed an arb exists, you need to know how much to bet on each side.

The Stake Formula

For each outcome, your stake should be:

Example: $1,000 Total Investment

Using our earlier 96.5% arb (Lakers +150 / Celtics -130):

Checking the Returns

If Lakers win (+150):
$414.51 × 2.50 = $1,036.28
Profit: $36.28

If Celtics win (-130):
$585.49 × 1.769 = $1,036.29
Profit: $36.29

Either way, you profit approximately $36 on a $1,000 investment—a 3.6% return with zero risk. Proper bankroll management helps you scale this strategy effectively.

Three-Way Arbitrage (Soccer, Hockey)

Sports with draws add a third outcome. The math is the same—just add a third implied probability.

Example: Premier League Match

• Sportsbook A: Liverpool +180
• Sportsbook B: Draw +260
• Sportsbook C: Arsenal +190

That's a 2% arbitrage margin across three outcomes. Soccer and other three-way markets often have more arb opportunities because of this added complexity.

Quick Reference: Common Odds Conversions

American Odds	Implied Probability
+300	25.0%
+200	33.3%
+150	40.0%
+100	50.0%
-100	50.0%
-110	52.4%
-150	60.0%
-200	66.7%
-300	75.0%

Why Manual Calculation Doesn't Scale

The math isn't complicated, but doing it manually across dozens of sportsbooks and hundreds of daily events is impossible. By the time you calculate and place bets, the odds have often moved.

That's why serious arbitrage bettors use automated tools that:

• Scan odds across up to 15 sportsbooks in real-time
• Calculate arbitrage percentages automatically
• Show exact stake amounts for each side
• Alert you when profitable opportunities appear

BetSuite does exactly this—scanning sportsbooks continuously and surfacing arbitrage opportunities with pre-calculated stakes. No spreadsheets required.

Key Takeaways

1. Arbitrage % under 100% = profit opportunity
2. Convert odds to implied probability first
3. Use the stake formula to size your bets correctly
4. Manual calculation works for learning, but tools are essential for execution
5. Speed matters—odds move fast