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Bet Expected Value Calculator

Enter your win probability, decimal odds and stake to find the bet's expected value.

How it is calculated

You supply your own estimate of the win probability as a percentage (0 to 100), decimal odds above 1.0, and the stake. Profit if the bet wins is stake × (odds − 1). Expected value is EV = p × profit − (1 − p) × stake, where p is the win probability as a fraction. EV % is EV divided by the stake, times 100. The implied probability is 100 / odds, the chance the odds price in. A positive EV means that, if your probability estimate is right, the bet pays off on average. The tool does not model several outcomes, a bookmaker's margin, bonuses, or stake returned on a push.

Worked example

You think a selection wins 40% of the time. The decimal odds are 2.8 and the stake is $50. Profit if it wins: 50 × (2.8 − 1) = $90. Expected value: 0.40 × 90 − 0.60 × 50 = 36 − 30 = $6.00. EV as a share of the stake: 6 / 50 × 100 = 12.00%. Implied probability of the odds: 100 / 2.8 = 35.71%. Your 40% is above 35.71%, which is why the EV is positive.

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Common mistakes

  • Typing the win probability as a fraction. Entering 0.40 is read as 0.4%, which makes almost every bet look hugely negative; type 40.
  • Using fractional or American odds. The tool needs decimal odds, which include the returned stake (5/1 is 6.0).
  • Treating the EV as a prediction for one bet. It is a long-run average; this single bet still wins or loses outright.
  • Copying the bookmaker's implied probability as your own. If your estimate is the implied figure, the EV is about zero and carries no information.
  • Entering the profit instead of the stake. The stake is the amount you risk, and the tool works out the profit from the odds.

About this calculator

Expected value (EV) in betting measures whether a wager is mathematically profitable over the long run, independent of whether any single bet wins. It's calculated as EV = (probability of winning × amount won) − (probability of losing × stake), comparing your own estimate of the true win probability against what the decimal odds imply the bookmaker thinks it is.

Decimal odds also encode an implied probability (1/odds), and the bookmaker's margin means the sum of implied probabilities across all outcomes exceeds 100% — the gap between your estimated probability and the implied one is exactly what determines whether a bet is +EV or −EV. This calculator computes the expected value in currency, as a percentage of stake, and the implied probability from your inputs — a standard tool for anyone studying sports betting or wagering math analytically rather than by gut feel; it's an educational calculation, not a guarantee of any outcome.

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Comments (1)

  • Editorial team

    Test how fragile the result is, because everything rests on your probability estimate. With odds of 2.8 and a stake of 50, each percentage point of win probability moves the expected value by stake times odds divided by 100, which is 1.40. A positive number built on a guessed 41 percent can vanish at 35. This is an educational calculation. What do you base your win percentage on, a model, past results or a hunch?

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