When two books disagree enough on a two-way market, you can back both sides and lock in a profit no matter who wins. Enter the best price you can get on each side to see if an arb exists, exactly how to split your stake, and the guaranteed return.
Pure arbs are rare and vanish fast. Scout hunts the more durable edge: markets priced wrong on the math.
Convert each side to decimal odds and take the reciprocals: 1/decimal_A + 1/decimal_B. If that total is under 1.00, an arbitrage exists — the two books combined are implying less than 100%, so backing both sides guarantees a profit. The gap below 1.00 is your edge.
To lock it in, split your stake in proportion to each side's implied probability so both outcomes pay the same. This calculator does that for you and shows the guaranteed profit whichever side wins.
The catch: real arbs are small, short-lived, and books limit or ban accounts that hammer them. It's a real edge — but a fragile one. KalEdge focuses instead on mispriced markets, where the math says the true probability differs from the price and the edge lasts longer than a refresh.