Fractional betting odds are most commonly used in the UK and South Africa. The fraction represents the fraction of your stake returned on a winning selection. For example 5/1, sometimes written 5-1 and is spoken as “five to one”, means that for every unit stake wagered you have the possibility to win five. With all reputable bookmakers you will pay your stake at the time of placing your bet, so this will also be returned on a winning selection. Meaning you will receive six stakes in this example.

Most regular punters can convert the most common of fractions to decimals in there head or remember them by heart. This is normally because working out most exotic bet types is many times easier when working with decimals. These decimal numbers are known as basic factors.

Example of fractions and there basic factor for the UK

Fractional Odds | Basic Factor |

1/4 | 1.2500 |

1/3 | 1.3333 |

2/5 | 1.4000 |

1/2 | 1.5000 |

4/6 | 1.6667 |

Even | 2.0000 |

11/10 | 2.1000 |

6/4 | 2.5000 |

2/1 | 3.0000 |

5/2 | 3.5000 |

3/1 | 4.0000 |

4/1 | 5.0000 |

In the table above all decimal prices are given to four decimal places, even when these numbers are redundant. This has come about because when betting returns were calculated by a human settler, four decimal places would make the betting odds and monetary value easily differentiated. Although with the growth of specially designed betting calculators this is no longer common practice.

It’s also worth noting that common fractional odds in South African
differ to that of the UK. They don’t have to handle large irrational
numbers; this is achieved by using fractional odds that have no more
than two decimal places. The UK systems maths is much harder and is
throw back to the days before decimalisation and the use of old money.
The use of just using the common basic factors is more prevalent with
the old school bookmakers. But now with the growth of internet betting
and the auto converting of decimal odds, it is becoming the norm to see
user unfriendly fractions.

## Converting Fractional odds calculations

Most commonly used fractional odds are easy to convert to decimal odds in your head. For example 5/2 can be seen as five halves. Which is 2.5 (5 x 0.5) and then plus 1 for the returned stake makes it 3.5 (unlike fractional odds decimal odds include the returned stake in the price)

But with the growth of the user unfriendly fractions, as mentioned above, this isn’t always that simple. For example 27/20. Calculating 27 twentieths in your head will probably just lead to a head ache. So get a calculator out and do the maths.

27 ÷ 20 = 1.35

Then add the returned stake of 1

1.35 + 1 = 2.35

So the maths to convert Fractions to decimals is

(Numerator ÷ denominator) + 1

Now we know how to convert fractions to decimals, the maths used to convert to American odds has become a little easier as we use this equation without the +1. There are two different calculations that will need to be used for this. One for when odds are greater than or equal to 2 (or Evens) and one for when odds are less.

For Fractional odds ≥ Evens, American odds = 100 x (Numerator ÷ denominator)

For Fractional odds < Evens, American odds = -100 ÷ (Numerator ÷ denominator)

## Converting Fractional odds examples

The calculations section has already given you one example of converting fractional odds to decimal odds but just to reinforce the maths we’ll show you one more example. But this example will show you a problem bookmakers have with their automatic odds conversions. The odds that need converting is 100/30 (this price is often called a Burlington Bertie as it sort of rhymes with the odds when said out loud, hundred to thirty). Now add this fraction to the equation.

(100 ÷ 30) + 1 = 4.333

So here the decimal odds are a recurring decimal. This gives the bookies a slight problem as they generally only offer odds to 2 decimal places. It is command to solve this problem by rounding up or down as is appropriate.

To demonstrate how to convert fractional odds to American odds we will need to show two examples as we need to see how both equations work. First the above evens example, 9/1.

American Odds = 100 x (9 ÷ 1) = 900

And for the second example below evens we’ll use 1/2.

American Odds = -100 ÷ (1 ÷ 2) = -200