True Odds Probability Calculator
Understand what an odd really means
Too many bettors place wagers without truly knowing what’s behind an odd. This calculator lets you instantly translate an odd into a percentage chance of success. It’s an essential tool for determining whether an odd represents genuine value or is overestimated.
You can also include the bookmaker’s commission (often overlooked), which distorts the true probability.
A simple, fast, and educational tool to improve your decision-making.
How it works:
- Enter the offered odd (decimal format).
- Choose whether to include the bookmaker’s margin (e.g. 10%).
- Click “Calculate probability.”
- You will see the true percentage chance of the event occurring.
- Use this percentage to compare against your own estimate (value bet?).
True Odds Probability Calculator
Discover the real chance of your bet winning
What does an American odd represent?
An American odd expresses the implied probability in a format tailored to payouts. Positive odds (e.g. +150) show how much profit you’d make on a $100 stake, while negative odds (e.g. –200) show how much you need to stake to win $100.
Formulas used:
If odds > 0: Probability (%) = 100 / (odds + 100) × 100 If odds < 0: Probability (%) = |odds| / (|odds| + 100) × 100
⚠️ Bookmakers include a margin to ensure profitability. That margin reduces the “true” probability the bettor faces.
The bookmaker’s margin: why include it?
To truly know the real chance of success, you must account for the bookmaker’s safety margin. Experts estimate it ranges between 5% and 15%.
This skews the “pure” odd and reduces the actual probability.
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An odd of +100 is no longer 50%, but about 45% with a 10% margin -
This helps you detect if an odd is unfairly high or low
Using this tool both with and without margin gives you a more realistic view of your “edge.”