What is the difference between fractional and decimal odds?

If you’ve ever watched horse racing on television or been lucky enough to go to the races live you will have seen and heard a barrage of numbers… 4/1, 7/2, 100/30 and so on. There are more fractions at the average horse meeting than in a GCSE maths exam. The same is true with online betting but the bookies you visit on your browser have another way of doing things – decimal odds.

This article is going to tell you the difference between fractional and decimal odds, when you’re likely to find them and what their relative strengths and weaknesses are.

Let’s begin with fractional odds. They are the traditional way that British bookmakers display their odds. Ever since the bookies started setting up at race courses they displayed their odds as fractions. When a bookie offers 5/1 on a horse, they are saying that you will win £5 for every £1 that you stake on the horse. As 7/2, you will win £3.50 for every £1 staked because you simply divide seven by two.

When looking at 3/1 or 100/1, fractional odds are very simple but they can get more complicated. If you’ve got 15/8 it can take a little bit of mental maths to work out how much money you’re going to win from a tenner. It’s also not immediately clear to everyone which is better value when weighing up two options, 27/20 or 11/8 for example. That is where decimal odds come in.

You won’t be shocked to read that decimal odds display odds as a decimal number rather than a fraction. The major difference between the two is the inclusion of the stake in decimal odds. With fractional odds of 3/1 you will win £3 from a £1 bet plus you will get your £1 stake back so a £4 total return. With decimal odds of 3.0 a £1 bet will return £3 in total – £2 profit plus your £1 stake.

As you can see 3.0 does not equal 3/1. If you want to convert fractional odds into decimals all you need to do is divide the fraction and add one. So 3/1 is three plus one, and you get decimal odds of 4.0. Fractional odds of 6/4 ((6/4)+1) becomes decimal odds of 2.5. Any decimal odds which are less than 2.0 are odds-on. So odds of 1/2 become 1.5, 10/11 equates to 1.91.

For many people decimal odds are much clearer and all of the main bookies now offer decimal odds on their site alongside fractional odds. But these ease of use is not the main reason that they were introduced, they grew in popularity in the UK thanks to the betting exchanges.

Many people use the betting exchanges like a stock broker would use the financial markets. Instead of betting on an outcome and waiting for the end of the event, they take a position and then trade it. This would be extremely difficult to do with fractional odds. When a price changes from 1.34 to 1.35, decimal odds show this clearly whereas the corresponding fractions would be complicated and difficult to read quickly.

In truth, it’s difficult to understand why people still use fractional odds other than for reasons of tradition. Decimal odds are easier to understand – especially at a glance – and offer bookies, punters and traders greater flexibility. The places where tradition still looms large over betting like the racetrack or betting shops will probably always stick with fractional odds but online the future is surely decimal.