betting arb calculator

What is a betting arbitrage?

Betting arbitrage (often called an “arb”) happens when different sportsbooks offer odds that, when combined, allow you to cover every possible outcome and lock in a profit regardless of result. The strategy is math-driven, not prediction-driven.

In plain terms: if the sum of the implied probabilities from your selected odds is less than 1.00 (or 100%), you have a theoretical risk-free edge before fees, limits, and execution risk.

How to use this calculator

• Choose a 2-way or 3-way market.
• Enter your total bankroll for this bet.
• Enter the best available decimal odds for each outcome.
• Click Calculate to get stake sizing, expected payout, and profit/ROI.

The tool computes the optimal proportional stakes so your payout is approximately equal across outcomes. That is the standard arb-sizing method.

Arbitrage formulas used

1) Implied probability

If the implied total is below 1.00, a positive arbitrage exists.

2) Stake allocation

This keeps returns balanced so the net result is nearly the same whichever outcome wins.

3) Return and profit

Quick example

Suppose a two-outcome event has odds 2.10 and 2.05 at different books, with a $100 total stake:

• Implied total = 1/2.10 + 1/2.05 = 0.9640
• Because 0.9640 is under 1.00, this is an arbitrage.
• Expected ROI ≈ 3.73% before operational friction.

2-way vs 3-way markets

Two-way markets are easier to execute because only two tickets are required. Three-way markets (e.g., home/draw/away) can still produce arbs, but the margin is often thinner and the timing risk is higher. For three-way opportunities, speed and accurate stake sizing matter much more.

Common mistakes to avoid

• Using mixed odds formats: convert everything to decimal first.
• Ignoring limits: one side may cap your bet and break the arb.
• Placing bets too slowly: lines can move between tickets.
• Forgetting fees/taxes: these can erase a small edge.
• Rounding too aggressively: small rounding errors can reduce guaranteed profit.

Practical execution checklist

• Confirm event, market, and settlement rules match exactly across books.
• Pre-calculate both stakes before placing the first bet.
• Place lower-liquidity side first to reduce incomplete-hedge risk.
• Track realized ROI after bonuses, commissions, and rejected tickets.

Final thoughts

Arbitrage is a disciplined numbers game, not a shortcut. The calculator gives the math instantly, but execution quality determines real-world outcomes. Use small test sizes first, build a process, and track every bet.

Please bet responsibly. Never risk money you cannot afford to lose.