Difference Between Decimal, Fractional and American Odds

As a gambler, you will encounter several different odds formats and your personal preference is likely to be based upon your location...

Dominic Field
July 21, 2021
July 21, 2021

As a gambler, you will encounter several different odds formats and your personal preference is likely to be based upon your location. If you were raised in North America, for instance you will naturally be more familiar with American odds. If you're a native of the UK, you probably prefer the more traditional fractional odds format. In this article, we'll help you to understand the differences between decimal, fractional and American odds.

What Are Odds?

Odds are primarily used as a way to express the probability of something happening. But they also indicate to abettor what their returns will be, if they place a winning bet. Odds can be displayed in a number of different ways, based on a mixture of personal preference and geographical location. Let’s take a look at the most common odds formats.

Fractional Odds

Used on the race tracks of the UnitedKingdom for centuries, this particular method of displaying odds remains popular with older gamblers, particularly in the high street betting shops. But younger bettors, who are more familiar with technology such as betting exchanges, are slowly moving towards decimal odds.

With fractional odds, the upper unit indicates the profit you'll receive when staking the lower unit. To calculate your profit, divide the top number by the bottom number and multiply by the stake. Then add the stake, because this is always returned on a winning bet.

Let's look at a couple of examples of fractional odds.

Example 1: 3/1

A bet of £50 at 3/1 would bring profit of £150, plus the original stake. That's £200 total returns.

(3/1) * 50 = 150

150 + 50 = 200

Example 2: 7/4

A winning £10 bet at 7/4 returns£27.50 in total (profit of £17.50).

(7/4) * 10 = 17.5

17.5 + 10 = 27.5

American Odds

These may be described as US odds,Vegas odds or even money line odds. Whatever you prefer to call them, you can spot American odds by the use of the plus and minus signs.

The positive number represents the underdog and shows your exact profit if you were to bet 100 units. The negative value, which is assigned to the favourite, indicates what you need to wager in order to win 100 units.

Here are some examples of American odds in action.

Example 1: +125

In this example, we are betting on the underdog. A $20 bet would yield a profit of $25 and returns of $45.

125 * (20/100) = 25

25 + 20 (the original stake) = 45

Example 2: -140

Here we are betting on the favourite, so the calculation is slightly different. A bet of $30 would return $51.43

(100/140 * 30) = 21.43

21.43 + 30 = 51.43

Decimal Odds

Originally a European odds format, decimal odds are now the preferred choice of many professional gamblers and serious bettors around the globe.

Not only do they allow for much more nuanced betting, when compared to other odds formats, but above all, it is far simpler to calculate your returns when using decimal odds.

To work out your potential returns, simply multiply the odds by the stake. Here's an example.

Example: 3.60

A €25 bet would return €90.

3.6 * 25 = 90

If you wanted to know the specific profit, rather than total returns, simply subtract the stake from this value:

90 - 25 = €65 profit

Asian Odds Formats

Although decimal, fractional andAmerican odds are the most commonly observed formats around the globe, there are still several others worth noting. Here is a quick summary of the variousAsian odds formats that you may encounter:

●     Indonesian - Indo, or Indonesian odds, are identical to American odds, but the number is divided by 100. So instead of-150, you would see -1.50.

●     Malaysian - Sometimes called Malay Odds, these are similar to Indonesian odds, only in reverse. Positive odds indicate the profit made from a stake of one unit. Negative numbers indicate the amount you need to bet in order to collect one unit of profit.

●     Hong Kong - These odds are essentially fractional odds, expressed as decimals. You can calculate Hong Kong odds by dividing the upper number of the fraction by the lower number. Or you can take regular decimal odds and subtract 1.

Converting Between Different Odds Formats

Unfortunately, there isn’t a simple formula to switch between all of the various different odds formats. The simplest conversion is undoubtedly fractional odds to decimal odds, which we will explain shortly. But for the most part, if you want to convert one format to another, you will need to use a conversion chart.

Convert Fractional Odds ToDecimal Odds

To change fractional odds into decimals is extremely simple. Just take the top number, divide by the bottom number and add 1. For example, converting 7/2 into decimal odds looks like this:

7/2 = 3.50

3.50 + 1 = 4.50

Convert American Odds ToDecimal Odds

Changing US odds into decimals can be done using either of the two calculations, depending on whether the American odds are positive or negative:

Positive US Odds

Use this formula to change positive American odds into decimals:

(Odds / 100) +1 = Decimal odds

For example,+250 in American odds looks like this:

250 / 100 =2.50

2.50 + 1 = 3.50

Negative US Odds

Use this formula to change negative American odds (ignore the negative symbol) into decimals:

(100 / Odds) +1 = Decimal odds

For example,-125 in American odds looks like this:

100 / 125 =0.80

0.80 + 1 = 1.80

Odds Conversion Chart

Here is a table featuring some of the most common odds, that will help you to switch between decimal, fractional and American odds formats.

Calculating Probability

Since the odds represent a probability of something happening, no matter which format is used, that means that you can calculate implied probabilities from the odds. If you are using decimal odds, you can deduce implied probability quickly and easily using the following formula:

Probability = 1 / Odds

Let’s work through a basic example. We know that when tossing a coin, the chances of it landing on one side or the other are exactly 50/50, or 2.00 in decimal odds. We can plug those numbers into the formula, to see if it holds true:

1 / 2.00 = 0.50

As you can see, the probability is0.50, or 50%.

So if the bookmaker’s odds as 7/4, we can work out the implied probability as follows:

First, convert 7/4 into decimal odds:

7/4 = 1.75

1.75 + 1 = 2.75

Then use the above formula to find the probability:

1 / 2.75 = 0.36

So the probability is 0.3636, or 36.36%.


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