Odds Converter
Convert a probability into the common odds formats.
Your numbers
Your results
Decimal odds
Decimal odds
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Fractional odds
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American odds
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Odds against : for
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Odds Converter by TheCalcTools
How the Odds Converter works
Enter the probability of the outcome as a percentage.
Decimal odds are the reciprocal of the probability.
Fractional odds are the chance of not happening divided by the chance of happening.
The formula
decimal = 1 ÷ pfractional = (1 − p) ÷ p
Worked example
Using the default values shown in the calculator:
| Probability (%) | 25 |
|---|
- Decimal odds = 100 ÷ 25 = 4.00.
- Fractional odds = 75 ÷ 25 = 3.000 to 1.
- American odds = +300.
Result:
| Decimal odds | 4.000 |
|---|---|
| Fractional odds | 3.000 to 1 |
| American odds | +300 |
| Odds against : for | 75.00 : 25.00 |
Frequently asked questions
What do the plus and minus signs mean in American odds?
A plus number is the profit on a 100 stake for an underdog. A minus number is the stake needed to win 100 on a favourite.
Do bookmakers' odds equal true probabilities?
No. Odds include the bookmaker’s margin, so implied probabilities usually add up to more than 100%.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.