Use this free arb bet calculator to split stakes across outcomes and check whether an arbitrage opportunity exists. Enter decimal odds from two or three outcomes, set your total bankroll for the trade, and the calculator will show stake sizing, implied probability, and expected locked-in profit (or loss).
Arbitrage Bet Calculator (Decimal Odds)
Ready to calculate.
Tip: A true arbitrage exists when (1/odds1 + 1/odds2 [+ 1/odds3]) < 1.
What is arbitrage betting?
Arbitrage betting (often shortened to “arb betting”) is a strategy where you place bets on all possible outcomes of an event at different odds so that your return is mathematically similar no matter what happens. If the combined implied probability is below 100%, you may have a positive edge and a theoretical guaranteed profit before fees, limits, or errors.
The core formula
For decimal odds, calculate the implied probability sum:
Arb Sum = (1/Odds A) + (1/Odds B) [+ (1/Odds C)]
- If Arb Sum < 1, there is a potential arbitrage opportunity.
- If Arb Sum = 1, it is break-even before friction costs.
- If Arb Sum > 1, the full hedge creates a mathematical loss.
Stake sizing
With total stake S, stake each outcome proportionally to its inverse odds:
- Stake i = S × (1 / Odds i) / Arb Sum
This equalizes payout across outcomes as much as possible.
How to use this arb bet calculator
- Select a 2-way or 3-way market.
- Enter your total stake budget.
- Input decimal odds for each outcome from your sportsbook(s).
- Click Calculate Arb to see stake splits, payout, and edge.
Example (2-way)
If odds are 2.10 and 2.05:
- Arb Sum = 1/2.10 + 1/2.05 = 0.9640 (96.40%)
- Since this is below 100%, it is a positive arbitrage setup.
If your total stake is $100, this tool distributes the stake so your return is balanced across outcomes and shows the projected profit percentage.
Common mistakes to avoid
- Slow execution: Odds can move before your second or third leg is placed.
- Incorrect market matching: Ensure all bets refer to the exact same event and ruleset (overtime included, void rules, etc.).
- Ignoring limits: Bookmakers may cap your stake and break your hedge.
- Rounding errors: Small stake rounding can slightly reduce guaranteed profit.
- Overlooking fees: Exchange commission, currency conversion, and withdrawal fees can erase slim edges.
Practical risk management
1) Keep records
Track each arb with timestamp, books used, odds captured, stakes submitted, and settlement result. Good logs help diagnose slippage and human errors.
2) Prioritize execution speed
Open all betting slips first, then submit in sequence with the hardest-to-fill leg first (usually the one with the lowest liquidity or strictest limits).
3) Focus on quality edges
Tiny theoretical edges can vanish quickly. Many bettors target larger percentage edges to better survive execution friction.
Final thoughts
An arb bet calculator is a sizing tool, not a guarantee of operational success. It helps you make mathematically sound stake decisions, but outcomes still depend on execution, market stability, account restrictions, and book-specific rules. Use the numbers, move carefully, and always double-check each leg before placing real money.