Odds Formats Converter

Convert Decimal, American and Fractional odds and see implied probability. Back to the calculator.

What this converter does

Paste odds in any format and we instantly convert to the other two and show the implied probability. Use it to compare prices across books that list different formats: for example -125 (American) ↔ 1.80 (Decimal) ↔ 4/5 (Fractional).

Formula recap: fractional a/b means decimal 1 + a/b. Probability is p = 1 / decimal. Positive American +A → 1 + A/100. Negative -A → 1 + 100/A.

Conversions: decimal ↔ American ↔ fractional. Probability p = 1 / decimal. Fractional a/b means decimal 1 + a/b. Minimum decimal supported: 1.01.

How to use this converter

1. Type into any one of the fields: Decimal, American or Fractional. The other two will auto-fill.
2. Input formats:
   • Decimal: accepts 1.80 or 1,80.
   • American: e.g. -125 or +200 (plus sign optional).
   • Fractional: a/b, e.g. 4/5 or 2/1.
3. The panel shows Implied probability (p = 1/decimal) and the Fair price in decimal odds.
4. Clear a field to reset the outputs.

Notes: numbers are rounded for display; fractional odds are approximated to a sensible denominator.

FAQ

Why does American show negative numbers?

Negative prices (e.g. -125) are favorites: you stake 125 to win 100. Positive (e.g. +200) means you win 200 for a 100 stake.

Why don’t fractional results look “clean”?

Some decimals don’t map neatly to simple fractions. We reduce to a sensible denominator; book displays may round differently.

Is implied probability the same as “fair odds”?

No. Books include margin. For no-vig probabilities/odds, use our No-vig guide.

More tools