Expected Value & Value Bet Calculator
Expected value calculator: compare your estimated probability with the one in the odds and get the difference, expected value and fair odds.
This value bet calculator (expected value calculator) compares your estimated probability with the one the odds imply and gives the difference, the expected value per bet and the fair odds from your estimate.
Expected value and value bet calculator
Compares your estimated probability with the one implied by the odds and gives the difference, the expected value and the fair odds.
The result is only as good as your estimate: a positive expected value on paper says nothing about any single result and takes many bets to show. This is not a recommendation to bet.
How it works
Enter the decimal odds, your estimated probability and the stake. If your probability is higher than the one implied by the odds, the expected value is positive; if it is lower, it is negative.[1] Expected value is an average over many repetitions, not what will happen on one particular bet.
Formulas
- Implied probability:
1 / D. Difference:p − 1/D. - Expected value per bet = stake × (
p × D − 1). - Fair odds from your probability:
1 / p.
Worked example
At odds 2.10, an estimated probability of 52% and a stake of 100: the implied probability is 47.62%, the difference +4.38 points, the expected value 9.20 per bet (9.20% of the stake) and the fair odds 1.92.
Things to keep in mind
- The result is only as good as your probability estimate; a small difference can be plain noise.
- A positive expected value says nothing about any single result and takes many bets to show.
- The bookmaker's margin is already inside the odds: where possible, compare your estimate with the no-margin probability.
Next steps
- First take the margin out of the price: the no-margin probability of the market is a cleaner reference than the raw odds.
- If you think a price is too high, what share of the bankroll Kelly suggests depends on how sound your estimate is.
- In a parlay the odds multiply, and so do the errors in your estimates: look at the combined odds of a parlay.
- A tip is not a probability; what a tip leaves out explains the difference.
Frequently asked questions
What is a value bet?
A bet where your estimated probability is higher than the one the odds imply. It depends entirely on your estimate being right.
How do you calculate expected value?
Probability × decimal odds − 1, multiplied by the stake.
What are fair odds?
The odds that match your estimated probability with no margin: 1 divided by the probability.
Does a positive expected value mean I will win?
No. It is a long-run average and only if the estimate is right; any single bet can lose.
To convert odds formats use the odds calculator.
18+. Take part only where it is legal. Betting carries a risk of loss. Do not treat potential returns as a budget and do not chase losses. If gambling stops being under control, stop and look for help from the support services in your country.
Notes and sources
- Wikipedia. Expected value. Checked on 05/11/2026.
