Fractional Odds Calculator

What Are Fractional Odds?

Fractional odds express the ratio of chances against success to chances for success. UK and European betting markets commonly use this format. For example, 5/1 means five chances to lose for every one chance to win. See also the Decimal Odds Calculator and Odds Probability Calculator.

Fractional Odds Formula

$$\text{odds} = \frac{C_{\text{against}}}{C_{\text{for}}}$$

where $C_{\text{for}}$ is the number of chances for success and $C_{\text{against}}$ is the number of chances against success.

Converting Fractional to Decimal Odds

Decimal odds equal $(C_{\text{for}} + C_{\text{against}}) / C_{\text{for}}$. To convert fractional odds $a/b$ to decimal, compute $a/b + 1$. For example, 5/1 fractional odds equal 6.0 decimal odds.