Expected value calculator
Provide a win probability and the net win/loss amounts for one stake. The calculator returns expected value with input validation and no stored defaults.
Calculator
Uses EV = p × (payout − cost − fees) − (1 − p) × (cost + fees). Inputs are not stored.
What this tool does
Expected value (EV) summarizes a single binary outcome stake when you already have an implied probability and the cash won or lost. It does not invent probabilities from titles or scrape live books.
Formula
`EV = p × netWin − (1 − p) × loss`, where `p` is in `0–1`, `netWin` is profit if the stake wins (stake returned separately if you model that way), and `loss` is the amount lost if it loses (usually the stake).
Limits
All inputs must be finite and non-negative where required; `p` must be in `[0, 1]`. Positive EV is not a recommendation to trade. Fees, spreads, and partial fills are out of scope unless you fold them into the win/loss amounts yourself.