Convert decimal, fractional and American odds to raw implied probabilities; optionally calculate complete-market overround and proportional shares.
How to use this tool
- Choose the event or model and review the assumptions below.
- Enter the labeled inputs.
- Select Calculate and read the labeled outputs.
- Change an input and calculate again; Reset restores the example inputs.
Calculation method
Raw implied probability = 1/decimal odds. For an exhaustive market, overround = Σraw−1; proportional normalization divides each raw probability by their sum.
Assumptions and limits
For overround and normalization, enter every mutually exclusive and exhaustive outcome from the same market. Normalized probabilities are a margin-removal convention, not established true chances or betting advice.
Worked example
Decimal quotes 2.00, 3.00 and 4.00 imply 50%, 33.3333% and 25%, summing to 108.3333%. If they cover a complete market, overround is 8.3333 percentage points. Proportional normalization gives approximately 46.1538%, 30.7692% and 23.0769%. The normalized values are a chosen margin-removal convention, not established event probabilities. Leave the market declaration at No when the outcome list is incomplete or uncertain.
Worked reading and practical questions
- Decimal, Fractional and American Odds: Keep Profit Separate from Return
- Market Overround and Proportional Normalization: What the Numbers Mean
Browse Statistics calculators or explore other tools on the GreenCalc homepage.
Frequently asked questions
What does this calculator assume?
For overround and normalization, enter every mutually exclusive and exhaustive outcome from the same market. Normalized probabilities are a margin-removal convention, not established true chances or betting advice.
How do I enter and update the inputs?
Use the labeled fields, then select Calculate. Percent fields use 0 to 100. After editing, calculate again; Reset restores the example inputs.