EV Calculator
Work out the expected value of a bet. Enter the price, your estimate of the true win probability, and a stake — get EV in dollars and percent, and how big your edge is over the book.
How expected value works
Expected value (EV) is the average amount a bet returns if you could place it an infinite number of times. It's the single most important number in betting: bet +EV consistently and you win long-term, bet −EV and the math grinds you down no matter how many individual bets hit.
The formula is:
EV = (win probability × profit if you win) − (loss probability × stake)
Worked example
You bet $100 at -110 (decimal 1.909) and believe the true win probability is 55%. Profit if you win is $90.91. So EV = 0.55 × 90.91 − 0.45 × 100 = +$5.00 — a +5% EV bet. The market's price implies only 52.4%, so your edge is 2.6 percentage points.
The hard part isn't the arithmetic — it's knowing the true probability. That's what a no-vig line from a sharp market gives you, and what PropPrizm computes automatically from a consensus of every book.
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
What is a good EV percentage in betting?
Anything above 0% is profitable long-term. In practice, edges you can actually find and beat the closing line on tend to sit in the 1–5% range on liquid markets; larger edges usually mean a stale line or an error in your probability estimate.
How do I find the true win probability?
The most reliable estimate is the no-vig (de-vigged) probability from a sharp market or a consensus of many books, rather than your own gut read. PropPrizm builds that consensus across every book automatically.
Is a +EV bet guaranteed to win?
No. EV is a long-run average. Any single +EV bet can lose; the edge only shows up over a large sample of bets, which is why bankroll management (see the Kelly calculator) matters.