Why do bookies use fractional odds?

fractional odds bookies

Sports betting odds are different in every part of the world. Most bettors are comfortable using the odd system they grew up with, no matter if it is more complicated than others.

Still, they always resume to probabilities, which can be estimated by calculating specific odds.

So, when it comes to sports betting odds, there are three types commonly used by bookies:

It seems like bookies from different regions want to theme their services to people who are using them.

When it comes to fractional odds, otherwise known as UK odds, it is worth mentioning that they are more complicated for calculating potential payouts, which is why many bookies transformed to decimal or American odds.

However, there are still many bookies, especially in the United Kingdom and Ireland that still use fractional odds. Fractional odds are one of the oldest forms of odds system that was originally used in horse racing.

 How to Calculate Fractional Odds?

Just so you can get a better idea of how fractional odds work and why bookies use them, we have to dig deeper and find out how to calculate them.

At first, fractional odds look like complicated math problems, once you understand how they work, calculating them is pretty easy.

The second number or the denominator (on the right) is the amount bet, and the first number on the left or the numerator is your potential winnings.

For example, a 10/15 fractional odd means that you need $150 in order to win $100 totaling $250 for a winning bet. If you need help to calculate these odds you can use the TwinSpires betting calculator here: edge.twinspires.com/betting-odds-calculator/

Why do Bookies use Fractional Odds?

Even though Fractional Odds are most common in the United Kingdom and Ireland, other parts of the world still use one of the oldest forms of odds. There are a few reasons why bookies use fractional odds.

Familiar to People

As we mentioned before, the sports betting system that people grew up with is what they prefer using. In the case of the United Kingdom, horse racing basically invented fractional odds and since then, people living there got familiar with this system.

The biggest reason why bookies use fractional odds is because of their customers. After all, the sports betting business wouldn’t be that much profitable if they provide services to people that don’t understand them.

Bettors Have difficult Time Calculating Probability of Fractional Odds

It is very important to understand that the odds don’t represent the probability of certain things happening in a sporting event. Bookmakers run a thorough analysis before any match, and they come up with probabilities.

These probabilities are then transformed into odds just to avoid giving you information about your chances of winning the bet.

However, most odd formats can be transformed into probabilities. When it comes to fractional odds, the formula for converting them into probability is difficult for most bettors.

Formula for Converting Fractional odds into Probability:

Denominator / (denominator + nominator) *100 = implied probability

For example, a 9/2 fractional odds probability can be calculated by:

2 / (2+9) * 100 = 18.1%

You can calculate the probability of fractional odds, but most bettors consider them more complicated. For bookies, it is best if bettors don’t know their chances of winning a certain bet.


Some of the biggest bookmakers from long-time ago are operating under the same rules and principles for hundreds of years. In other words, some of the biggest sports betting houses from a long-time ago grew to be one of the biggest bookmakers in the world.

Most of them stick to their roots by maintaining the same odds system. Since some of the world’s biggest bookies come from the United Kingdom, they still use fractional odds. When the biggest bookies use fractional odds, chances are more bookies will start accepting them.

Final Thoughts

There is no doubt that fractional odds are one of the most popular odds formats in the world. Since they are used by some of the world’s largest bookmakers, they are one of the preferred odds for sports bettors across the world.

The only difference between the odd formats is how you calculate them. They are a pale interpretation of chances of certain things happening in a sporting event which are not accurate at all times.

Although betting has its fair share of luck, having knowledge of probabilities and being aware of the stats, especially on sports (player and team’s form, home advantage, etc) it’s very important to predict an outcome that will give you profit.

Nonetheless, it is up to you to choose which odds format you are most comfortable with and there are no certain advantages or disadvantages to each of them. Remember you can find betting calculators online that will help you in determining probabilities.