Calculating Betting Odds To Help You Win More

When you understand betting odds and percentages your profits will increase. By thinking of the Modus Operandi (MO) of the bookmakers, and putting yourself in their shoes then you can start to see what they are up to with individual prices.

Calculating Betting Odds To Help You Win More

Understanding Betting Percentages

When you understand betting odds and percentages your gambling has a better chance of being profitable. 

By thinking of the Modus Operandi (MO) of the bookmakers, and putting yourself in their shoes then you can start to see what they are up to with individual prices.

The OLBG article on understanding bookmakers will give you further and valuable insight into how they think and work.

The Executioner in his excellent Bookmaker Betting Percentages blog explained how each price is equal to a percentage.

Here is a fictional example of a 5 runner horse race. 

Betting Odds Betting Percentage
2/1 33.33%
3/1 25%
7/2 22.20%
5/1 16.67%
8/1 11.11%

If you add up the 5 percentage figures you get to a percentage of 108.33%. 

Whichever horse wins the bookmakers will make a profit because of the percentage being above 100%.

They will adjust these odds as money comes in for each horse, enabling them to always keep the percentage above 100%.

The Racing Post each day publishes the betting percentages of each race and you can see the variation of betting odds/percentages between bookmakers.

For example, Paddy Power may have the biggest percentage book at 110%, and Bet Victor may have the smallest percentage book at 107%. 

The 10% and 7% above 100% are the bookmakers overround, - their margin. 

Bookmakers Overound or Margin

Why not calculate the bookmakers margin from a set of matches or horse races. It will give you insight as to how the bookies are thinking about the event.

The overround is the bookie's advantage and is calculated so they will collect more from punters than they will pay out to punters - they do this for every betting event. 

You will never see a percentage overround under 100% from a bookmaker, why would they price up an event to lose money!

The smaller the individual price the bigger the percentage, the bigger the individual price the smaller the percentage.

By always choosing the best price on offer and being strict with only getting the best price this will help in our aim of beating the bookies by reducing their % overround.

I repeat this because you always need to remember "The smaller the price the bigger the percentage, the bigger the price the smaller the percentage."

Below you can see sample odds and the overround in a football match. 

How To Convert Decimal Odds into Fractional Odds

To convert decimal odds to fractional:

(Example Betting Odds of 3.75:  Take away 1.00. Therefore 3.75 - 1.00 becomes 2.75/1 or 11/4.)

To convert fractional odds into decimal odds:

(Example Betting Odds of 11/4: Divide the first figure (11) by the second figure (4) =2.75. Then add 1.00 =3.75 therefore 11/4 = 3.75.)

So with the 3 football prices below the best odds from different bookies give an overround of 101.5% or 103.14%. 

Paddy Power - 101.5%

Results Decimal Odds Fractional Odds Betting Percentage
Arsenal 2.55 31/20 39.21%
Draw 3.12 85/40 32.00%
Manchester United 3.30 23/10 30.33%


However only using Bet Victor for all three prices and the percentage overround as you can see is bigger.

BetVictor -103.14%

Results Decimal Odds Fractional Odds Betting Percentage
Arsenal 2.45 29/20 40.81%
Draw 3.12 85/40 32.00%
Manchester United 3.30 23/10 30.33%


If over a year you make sure that these small percentage differences are in your favour you can have an extra 1% or 2% each time you bet, losses can be reduced and profits increased.

By taking the best prices from different bookmakers and exchanges you can create a betting book that is LESS than 100%.

This means you can back all three outcomes in a football match (HDA) or all runners in a horse race and be guaranteed a profit before the match has kicked off or race has been run. 

Use the OLBG Betting Tips pages to find the best odds on an event, you will then see the difference it makes in taking the best bookmaker prices.

Betting Percentages Recap

  • 1. Check the bookmakers event percentage.
  • 2. Compare and contrast bookmakers individual percentages.
  • 3. Always take the best prices on offer. Use different bookmakers.
  • 4. Practice decimal and fractional odds calculations.

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