Arbitrage
An arb exists when two books price the two sides of a market so far apart that backing both guarantees a profit no matter the result. Enter the best price on each side from two books and a total budget. If the implied probabilities sum below 100 percent, we size each leg so both outcomes return the same, and show the locked profit. Real arbs are small, brief, and can get your account limited, so treat this as a check, not a strategy.
Arb if 1/decimalA + 1/decimalB < 1 · stakeᵢ ∝ 1/decimalᵢ · profit % = 1 − (1/decA + 1/decB)
Books move fast and limit arbers. A line can change before both bets are placed, turning a guaranteed profit into one-sided exposure.
Market-neutral utility. It computes numbers you supply, it does not predict outcomes or guarantee profit. Compare lines across books and make the call yourself. 21+ · research, not advice.