How to use this betting tool
- Enter each value using the unit shown beside the field.
- Select Calculate to validate the inputs and update every result.
- Compare the main result with the supporting figures and read the stated limitation before using it.
#041 · Odds Probability & Margin Tool
No-Vig Probability Calculator
Remove proportional bookmaker margin from two decimal odds and compare implied probabilities, fair probabilities, fair odds, and market overround.
Calculator
Enter assumptionsDecimal
Decimal
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What this tool calculates
Remove proportional bookmaker margin from two decimal odds and compare implied probabilities, fair probabilities, fair odds, and market overround.
Implied probability = 1 ÷ decimal odds. Proportional no-vig probability = implied probability ÷ the sum of all implied probabilities.
Inputs are processed locally in your browser. Verify market definitions and settlement terms before relying on a result.
Worked example
At odds 2.50 and 1.67, the raw probabilities total about 99.88%. Proportional normalization makes the two fair probabilities add to exactly 100%.
| Check | Meaning |
|---|---|
| Inputs | Use the values described above |
| Output | Recalculate in the tool to reproduce the example |
Tips and limitations
- Use decimal points, not commas, inside number fields.
- Keep inputs from the same market, time period, and unit.
- Treat model estimates as assumptions rather than observed probabilities.
- Check operator-specific rounding and settlement rules.
FAQ
How is the no-vig probability calculated?
Implied probability = 1 ÷ decimal odds. Proportional no-vig probability = implied probability ÷ the sum of all implied probabilities.
Does the result include bookmaker margin?
Only when the displayed formula explicitly uses market odds. Model probabilities and projections are based solely on the values entered.
Why can my bookmaker settlement differ?
Operators may use different rounding, void, dead-heat, minimum-stake, or market settlement rules. Check the rules for the specific bet.
How much precision does the calculator use?
Calculations use JavaScript floating-point precision and are rounded only for display, normally to two or four decimal places.
Can this result predict a winning bet?
No. It calculates a mathematical scenario from your inputs and does not account for every source of uncertainty or guarantee an outcome.
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Result guide
| Measure | Use |
|---|---|
| Outcome A fair probability | Primary calculated value |
| Outcome B fair probability | Supporting cross-check |
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