Enter your stake, true win probability, and the offered odds.
Pure math only. Not financial advice; no real-money handling.
About this tool
The Expected Value (EV) Bet Calculator tells you whether a wager is profitable in the long run by comparing your own estimate of the true win probability against the price the book offers. On a win you profit stake × (decimal − 1); on a loss you forfeit the stake. Weighting each by its probability gives the expected value: EV = p × stake × (decimal − 1) − (1 − p) × stake, which simplifies to the clean form EV = stake × (p × decimal − 1).
The tool also reports EV% per unit staked, (p × decimal − 1) × 100%, and flags the bet as +EV, −EV, or neutral. A positive result means the price is better than your assessed fair value and the bet gains money on average; a negative result means the opposite. For reference it shows the fair decimal odds implied by your probability, 1/p, alongside the offered price — if the offered odds exceed the fair odds, you have an edge. Betting 100 at decimal 2.00 with a true 55% win chance gives EV = 100 × (0.55 × 2.00 − 1) = 10, a +10% edge.
All computation is done locally in your browser and nothing is uploaded. This is a pure arithmetic tool — not financial or betting advice, and no real money is handled. The result is only as reliable as your probability estimate.
Frequently asked questions
How is expected value calculated for a bet?
EV = stake × (p × decimal odds − 1), where p is your true win probability. It combines the profit on a win, stake × (decimal − 1), weighted by p, with the loss of the stake weighted by (1 − p). Positive EV means the bet gains money on average.
What does +EV mean?
A +EV (positive expected value) bet is one where p × decimal > 1 — the offered price is better than your fair estimate, so you expect to profit over many identical bets. −EV means the reverse, and neutral means the price exactly matches your fair value.
What are the fair odds shown?
Fair odds are the break-even decimal price for your probability, 1/p. If p = 55%, fair odds are 1/0.55 ≈ 1.82. When the offered odds are higher than the fair odds you have positive expected value; when they are lower the bet is −EV.
How accurate is the EV result?
It is only as good as your win-probability estimate. EV is a mathematical expectation over the long run, not a prediction of any single bet, and a wrong probability produces a misleading EV. Use realistic, well-researched probabilities.
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