Arbitrage calculator
Updated August 2026
Two books, two opinions, one guaranteed profit — if the numbers truly disagree. Check before you leap.
+$11.75
guaranteed profit
Under 100% combined means the books disagree enough to pay you the gap. Real arbs are rare, small, and vanish fast.
How the split is sized
Stakes are divided in proportion to each side's implied probability, so both outcomes pay exactly the same total. When the two books' chances sum under 100%, that identical payout is bigger than your combined stake, and the difference is yours regardless of the result. That's arbitrage: profit from disagreement rather than prediction.
Why arbs are rare and shy
Every arber is racing every other arber, and the books' own traders, to close the same gap. Real arbs are small, brief, and hazardous to your account standing. The same idea appears on prediction markets when two venues price one question differently, which is legal to exploit and equally quick to vanish.
Quick answers
What is arbitrage betting?+
Backing both sides of the same event at two different books whose odds disagree enough that you profit whichever way it lands. It exists because books move lines at different speeds.
How do I know if an arb exists?+
Convert both odds to implied probability and add them. Under 100% combined is an arb, and the gap is your margin. Over 100% is just two books charging normal vig.
What's the catch?+
Books aggressively limit and close accounts that arb, lines move while you're placing the second leg, and a voided bet on one side leaves you fully exposed on the other. The math is free; the execution is not.