Arbitrage Calculator
Detect arbitrage opportunities across sportsbooks and prediction markets. Calculate optimal stake allocation and guaranteed profit with platform fee adjustments.
Market Setup
Outcomes:
Frequently Asked Questions
What is sports betting arbitrage?
Arbitrage (or "arbing") exploits pricing differences between bookmakers or prediction markets. When the combined implied probabilities of all outcomes across different platforms sum to less than 100%, you can bet on every outcome and guarantee a profit regardless of the result.
How do I find arbitrage opportunities?
Compare odds for the same event across multiple sportsbooks or prediction markets. Calculate the arb index (sum of 1/decimal for each outcome). If it is below 1.0, an arbitrage exists. The Odds Reference dashboard tracks cross-platform pricing in real time to help identify these opportunities.
What is the arb index?
The arb index is the sum of the inverse decimal odds for each outcome (1/decimal_1 + 1/decimal_2 + ...). If the index is below 1.0, arbitrage exists and the profit percentage equals (1/arbIndex - 1) × 100. An index of 0.97 means a guaranteed 3.09% return.
How much can I profit from arbitrage?
Typical sports arbitrage opportunities offer 1-5% returns per event. Prediction market arbitrage can occasionally yield higher margins due to less efficient pricing and cross-platform fragmentation. Returns are reduced by platform fees, which this calculator can factor in.
Do platform fees affect arbitrage profitability?
Yes. Fees can eliminate thin arbitrage margins entirely. Kalshi charges a formula-based fee, Polymarket US charges 0.1% per trade, and other platforms have their own structures. Enable the fee toggle in this calculator to see adjusted profits.
Can I arbitrage prediction markets?
Yes. Cross-platform arbs between Kalshi, Polymarket, and other exchanges are possible when the same event is priced differently. Enter contract prices in PM Cents format and select the platform for each outcome to see fee-adjusted returns.
Is arbitrage betting legal?
Arbitrage betting is legal in most jurisdictions. However, sportsbooks may limit or close accounts of bettors they identify as arbers. Prediction market exchanges generally do not restrict arbitrage activity, though terms of service vary by platform.
How do I calculate optimal stake allocation?
For each outcome, the optimal stake equals: (total investment × 1/decimal_i) / arbIndex. This ensures the payout is identical regardless of which outcome wins. The calculator computes this automatically and shows a detailed stake allocation table.