Odds Converter & Implied Probability Calculator
Convert between decimal, fractional and American odds, and see the implied probability and potential profit. Calculations run in your browser — nothing is sent anywhere.
The formulas
- Fractional → Decimal: Decimal = (numerator ÷ denominator) + 1
- American (positive) → Decimal: Decimal = (American ÷ 100) + 1
- American (negative) → Decimal: Decimal = (100 ÷ |American|) + 1
- Implied probability: 1 ÷ Decimal odds, shown as a percentage
- Potential return: Stake × Decimal odds
Worked example
Decimal odds of 2.50 imply a probability of 1 ÷ 2.50 = 40%. A $10 stake would return $10 × 2.50 = $25 (a $15 profit). The same price is fractional 3/2 and American +150.
Implied probability does not represent the actual probability of an event occurring. It reflects the price offered, including the bookmaker's built-in margin. This tool performs mathematics only and is not betting advice.
Tools
Frequently asked questions
Does implied probability tell me the real chance of something happening?
No. Implied probability does not represent the actual probability of an event occurring — it only reflects the price offered, which also builds in the bookmaker's margin. Treat it as a reference point, not a forecast.
Why do American odds need a value of at least 100?
By definition, American odds only express prices at or beyond even money — positive odds start at +100 and negative odds start at -100. Values between -99 and +99 aren't valid American odds.
Why might the fractional conversion look unfamiliar?
This tool converts your decimal odds into their exact mathematical fraction, simplified — bookmakers often display a nearby 'round' fraction instead (like 6/4 rather than an exact equivalent), so the two can differ slightly in presentation while being mathematically equivalent.