Fractional, Decimal and American odds
Depending on where you are geographically, odds can be expressed in any one of three ways, each very different from the others. This often means that working the odds can be tricky unless you understand what they are expressing.
Fractional odds, also known as English odds, are the oldest way of expressing odds and do so as a fraction. The right hand figure in fractional odds represents the stake while the left hand figure represents the winnings.
For example 10/1 would mean that a stake of 1 would yield winnings of 10, for a total return of 11 including the original stake.
More complex examples however aren't nearly so easy to calculate, particularly if the stake is different to the number expressed in the odds and won't divide evenly
For example 12/5 would mean that a stake of 5 would result in winnings of 12, however with a different stake this isn't easy to work out. That being the case converting the fraction into a decimal is generally the easiest way of calculating it (see below).
Decimal odds are the easiest and simplest odds to calculate due to the fact that they are simply multiplied by the stake to give total returns. For example decimal odds of 4.5 and a stake of 2 would be expressed as follows:
2 (stake) x 4.5 (odds) = 9 (total return)
American odds are perhaps the most complicated of the three systems to understand and are based on how much one would have to stake in order to achieve a return of 100. American odds are expressed with a + or - in front of them are are shown in units of ten.
A plus sign in front of an odd represents how much a stake of 100 would return, so for example:
+650 would return winnings of 650 with an initial stake of 100.
A minus sign represents how much would need to be staked in order return winnings of 100. So for example -220 would mean that 220 would need to be staked in order to return winnings of 100.
Perhaps the easiest way of calculating fractional odds if you aren't used to them is to convert them into decimal odds instead.
In order to do this simply add the two figures of the fraction together and divide by the right hand number. For example:
10/3 10+3=13 13 divided by 3 = 4.33
We are then left with a decimal figure which can be multiplied by a stake figure to calculate a return.
Converting American odds to decimals
Although a little more complicated, American odds can also be converted to decimal odds fairly easily, making them much easier to calculate.
For positive odds, ie those with a + sign next to them, we simply add 100 to the American odds figure and then divide by 100. So for example odds of +550 would look like this:
+550 + 100 =650 650 divided by 100 = 6.5
For minus odds we divide 100 by the American odds and add one. For example using -220 as an example:
100 divided by 220 = 0.45 0.45 + 1 = 1.45