# Useful Formulae – Quick formulae for odds comparisons and percentage chances. To convert odds into a percentage chance

(2nd part of price/Total of both halves of price) x 100 = percentage chance

Worked example: 6/4

4/10 x 100 = 40%

To convert a decimal price into a percentage chance

(1/decimal price) x 100 = percentage chance

Worked example: 2.50

1/2.50 x 100 = 40%

To convert a percentage chance into a decimal price

100/percentage chance = decimal price

Worked example: 40%

100/40 = 2.50

To convert a percentage chance into odds/1

(100/percentage chance) -1 = odds/1

Worked example: 40%

(100/40) -1 = 1.50/1

Balance your bets and lays with this conversion chart

Each line is designed to break even to a total outlay of £100.

Beat The Book – An Application of Mathematics

Here is a mathematical technique to help you convert any race into a profitable scenario by writing off the chances of the contenders which, in your opinion, cannot win.

At first, the technique will work best in early price races because you will have the time to make your calculations without fear of prices changing in midstream.

First of all, study a race and delete all the runners that you are convinced cannot win.

Next, you will need to carry out the following calculations on the prices of the live contenders you have selected – I have tabulated an example to make the explanation easier.

The example shows a list of selected ‘live contenders' in a race, together with the best early prices available for each:

*To express in terms of chance, use the second half of the odds fraction and the total of the odds fraction.

E.g., 15/8 would be 8 chances in 23 (15+8)

We can see that, by staking the calculated amounts to win on each of our live contenders at the best early prices we can find, we are certain of securing a £12.19 profit (13.88% ROI) regardless of which contender wins. We are confident of the outcome because we consider the runners we have eliminated to have no chance of winning.

Obviously you cannot use the technique if the sum of your percentages is more than 100. However, should you decide to eliminate a well-fancied favourite from your calculations, or your list of live contenders is very short, the potential profit can be significant.

The technique can be used in a live betting market once you become so familiar with the calculations that you are able to make them very quickly.

These calculations can be carried out extremely quickly and efficiently by using the Beat The Book tool.

Steve Jones

Professional Betting Advice and Strategy (2000-22)