Betting Odds Explained

fractional odds
A typical example of odds shown on bet365

When getting to grips with the foundations of sports betting, arguably the thing that confuses people most is the odds. For those looking for a simple betting odds explained guide, look no further, as we break down how odds work and how you can utilise them when betting on sports.

Breaking it down to its most basic level, betting odds are simply a numerical representation of the chance of a certain outcome happening.

Chance (or probability) can be written as a percentage, or in our case, as decimal or fractional odds.

As an example in this betting odds guide, if you were to take a 6 sided dice, the probability of you rolling a 3 would be 1 in 6 – this effectively means on average, you’d have to roll the dice 6 times to get your desired number (in this case, a 3).

As a percentage, this would give us a 16.67% chance of rolling the 3.

How is this calculated? Simple – you take 100%, which would theoretically be the probability of any number on the dice landing and dividing it by 6 (the number of possible outcomes).

100% ÷ 6 = 16.67%

Decimal Odds Guide

Outside of the UK and US, it has become common practice by online bookmakers to display odds in a decimal format. This is typically the most easy to understand method and makes finding the highest odds price on a comparison site very simple – in essence, a larger number equals larger returns.

Essentially the percentages we mentioned in the previous paragraph of this betting odds guide would be converted into a number as per this instance below.

Continuing with the dice example, we’ve established that the probability of rolling a 3, or indeed any number on the face of a dice is 16.67%. To find out what this would be in decimal odds, you can use the following formula:

100% ÷16.67%= 6.0

Applying this to a real life betting scenario, should Real Madrid have a 20% chance of winning this season’s Champions League, their decimal odds would equate to 5.0 (100%÷20%).

From a betting point of view, should you think Madrid’s chances of winning the Champions League are greater than 20%, then odds of 5.0 would be seen as favourable.

Fractional Odds Guide

Whenever you see two numbers that are separated by a slash, these are known as fractional odds. There are several ways of explaining how these work, but the simplest would be to see the number on the left as how much you could win and the number on the right as how much you’d need to stake.

As an example, if Manchester United were a price of ‘5/2’ to beat Chelsea on any given weekend, then someone staking £2 would in theory, win £5. Using the odds provided, you can calculate how much you stand to win should you bet on Manchester United in relation to your stake using the following formula.

(Your stake (i.e. £10) ÷ the number on the right) X the number on the left = your returns

In the case of the Manchester United bet of 5/2, your returns from a £10 stake would be as follows:

(£10 ÷ 2) X 5 = £25

Whilst all bookies will usually calculate your returns for you, being able to spot which fractional odds are higher is of paramount importance when trying to get the best price on odds comparison sites. If you were to see a rival bookmaker is offering odds of Manchester United to win at 9/4, you could use the same formula to calculate which price would garner the highest returns. We already know a £10 stake would result in £25 winnings at 5/2, but how much could we win should we take the rival bookmaker’s odds at 9/4?

(£10 ÷ 4) X 9 = £22.5

Once you gain experience working with fractional odds, it will become second nature deciphering which set of odds will garner the highest returns. Many experienced bettors instantly know the difference between 5/2, 9/4 or indeed 3/1 for example. It is for this reason, over many decades that punters in the UK still prefer fractional odds over decimal odds.

By Manchester United being priced at 5/2 to beat Chelsea, the bookmaker is essentially saying that should these two teams play each other 7 times (5+2), that Manchester United should be expected to win 2 times and not win (draw or lose) 5 times.

It’s from this basis that your winnings are calculated from fractional odds.

American Odds

For foreign eyes, US odds are perhaps the most difficult to understand. US odds, in essence, work by showing you how much you’d need to stake to win $100 OR how much money you will make if you stake $100. A negative number with a minus sign next to it would indicate how much you’d need to stake for $100 in winnings whilst a positive number with a plus sign would indicate how much a $100 stake would get you.

As an example in this odds guide, if an NBA basketball team were priced at -250 to win a particular match, then this means you would have to stake $250 in order to win $100.

However, if their opposition were priced at +250, this would mean a $100 stake would net you $250.

In both instances, this can easily be converted into decimal odds using the following formula:

Positive odds: (250/100) + 1 = 3.50

Negative odds: (100/250) + 1 = 1.4


For all intents and purposes, beginners should stick to decimal odds when trying to find their way in the complicated world of online sports betting. As already stated in this sports betting odds explained guide, with many if not all bookmakers offering decimal odds on their sites as standard, there isn’t a drastic need for the use of fractional odds. The only exception would perhaps be on UK and Irish horse racing – a segment of sports betting in which traditional fractional odds has stood the test of time.


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