Arbitrage Calculator
Check whether two prices on opposite outcomes lock in a guaranteed profit, and how to split your stake across the two books. Enter both prices and your total bankroll for the play.
How arbitrage betting works
An arbitrage ("arb") happens when two books price opposite outcomes so generously that you can bet both sides and profit no matter what. It exists when the implied probabilities of the two outcomes add up to less than 100%.
Split your stake in proportion to each side's implied probability so both outcomes return the same amount:
stake on A = total × (1/decimal A) ÷ (1/decimal A + 1/decimal B)
Worked example
Book 1 has A at +110 (2.10), Book 2 has B at +105 (2.05). Implied probabilities: 47.6% + 48.8% = 96.4% — under 100%, so it's an arb worth about 3.7%. On $1,000 you'd stake ~$506 on A and ~$494 on B for ~$37 guaranteed.
Arbs are rare, small, and books limit accounts that hit them. A steadier edge is finding one soft price versus fair value — which is what the EV+ board does.
Stop doing this by hand
These calculators do one bet at a time. PropPrizm's EV+ board runs the de-vig and EV math across every book, on every prop, live — and surfaces only the ones where a book is soft versus the market consensus.
See the EV+ board →Frequently asked questions
Is arbitrage betting legal?
Arbitrage betting is legal, but sportsbooks discourage it and will limit or close accounts they suspect of arbing. It is not against the law; it is against most books’ terms of preferred use.
Why are arbitrage opportunities so small?
Books price efficiently and adjust fast, so genuine arbs are usually a fraction of a percent and disappear quickly. After the effort and account risk, many bettors prefer +EV betting for a larger, more durable edge.
How do I split my stake for an arbitrage?
Stake each side in proportion to its implied probability so both outcomes return the same total. The calculator above does this automatically from your total stake.