How to use this betting tool
- Enter the amount risked and decimal odds.
- Add your independently estimated chance of winning.
- If applicable, enter commission charged only on net winnings.
- Calculate and compare EV with zero.
#091 · Odds Probability & Margin Tool
Expected Value Betting Calculator
Compare your own win-probability estimate with the price on offer. This calculator shows the average profit or loss implied by those assumptions—not a prediction of the next result.
Calculator
Enter assumptions$
x
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What this tool calculates
Expected value weights the net win and full-stake loss by their probabilities. It is a long-run average under the probability entered, not a guaranteed result.
Net win = stake × (odds − 1) × (1 − commission). EV = p × net win − (1 − p) × stake.
Commission is assumed to apply to positive winnings only. Taxes, voids and partial settlements are excluded.
Worked example
At $100, odds 2.20 and a 50% win estimate with no commission, the weighted profit is $10 and expected ROI is 10%.
| Win branch | $120 profit × 50% = $60 |
|---|---|
| Loss branch | −$100 × 50% = −$50 |
| EV | $10 |
Tips and limitations
- Your probability estimate is the most sensitive input.
- A positive EV can still lose repeatedly.
- Use the same commission basis as your exchange or bookmaker.
FAQ
How is betting expected value calculated?
Multiply each possible net profit or loss by its probability, then add the weighted outcomes.
Does positive EV mean the bet will win?
No. It means the assumptions imply a positive long-run average; any individual bet can lose.
Is stake included in decimal-odds profit?
No. Net win is stake multiplied by decimal odds minus one; the returned stake is not profit.
How does commission change break-even probability?
Commission reduces the net win, so a higher win probability is required to break even.
Should I use bookmaker implied probability?
EV is useful only when the probability is your own justified estimate; reusing the offered implied probability normally reproduces the price.
Related betting tools
EV interpretation
| EV above 0 | Positive under entered assumptions |
|---|---|
| EV equal to 0 | Break-even |
| EV below 0 | Negative under entered assumptions |
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