Converting Betting Odds

The odds convertor tool in this page will convert odds from any of the three main formats into the other formats. It will also calculate the relevant implied probability too. To use it, simply enter the odds you wish to convert in the appropriate box, and then click the "Convert Odds" button. It's as easy as that!

American Odds:
Decimal Odds:
Fractional Odds:
Implied Probability:

If you came to this page specifically looking for a tool to convert odds, then it's likely that you already have a fundamental understanding of what odds are and how they work in relation to sports betting. If this is a subject that you're not particularly familiar with, however, then you might want to read the following article from our beginner's guide to sports betting.

Overview of Different Odds Formats

If you live in the United States, then simply knowing the moneyline odds will suffice, as this is the primary format used by the limited number of gambling sites available for US residents. Likewise, if you live in the United Kingdom, then you only really need to know how fractional odds work. If you live in Europe, then the decimal format is the one that will be most important for you to understand.

With all that being said, it's still a good idea to be familiarized with how each format works. Many online betting sites will allow you to choose the format that their odds are displayed in. Please keep in mind that the conversation may round in their favor.. For example, most US friendly sites offer moneyline odds of -110 when betting points spreads. If you choose to bet in the decimal format instead, then you'll often be given odds of 1.90. The true conversion is 1.9091 though, so you'll potentially lose a small percentage of your winnings if you bet based on their conversion.

Therefore, it can be an advantage to use the primary format offered by an online bookmaker, which is why it pays to make sure you understand each of the different formats. We've explained them all below for you.

American Odds/Moneyline Odds

Odds in this format are expressed as either a positive number or a negative number. When they are a positive number, the number represents how much in winnings is paid per $100 staked. The following examples illustrate how positive moneyline odds work.

When they are a negative number, the number represents the amount of money that needs to be staked in order to win $100. The following examples illustrate how negative moneyline odds work.

Please see our article on calculating payouts from moneyline odds for details on how to work out the potential winnings from wagers using this format.

Decimal Odds

This is the most popular odds format outside of the United States and is sometimes referred to as European odds. It's a very simple format where the odds are expressed as a single positive number, usually to two decimal places. This number states how much a winning bet returns (including the initial stake) for each unit wagered. The following examples illustrate the decimal format in practice.

Our article explaining how to calculate payouts from decimal odds will teach you how to work out the potential returns from wagers placed using this format.

Fractional Odds

Fractional odds are mostly used in the UK, but lately the decimal format has been becoming more popular. Odds in this format are displayed as a fraction, as the name suggests. The first number of the fraction shows how much you can win per the second number staked. This sounds more complicated that it actually is and the easiest way to understand this format is simply to look at some examples.

Please note that when the second number of the fraction is higher than the first, it means the odds are less than even money. This is referred to as odds on (as opposed to odds against), and is the equivalent of when moneyline odds are a negative number or when decimal odds are a number less than 2.

Odds Conversion Math

Our conversion tool is the easiest way to change odds between formats but there will be times when you don't have access to it. When you're at a Las Vegas sportsbook or a high street bookmaker, you may need to be able to do these conversions in your head. For this reason, we'll run through the math required to convert each format into all of the other formats.

Converting Moneyline Odds

To Decimal

The calculations required to convert from moneyline odds changes depending on whether the odds are positive or negative. To convert positive odds into decimal odds, the following calculation is required.

(Moneyline Odds + 100) / 100 = Decimal Odds
Example: Converting +175
(+175 + 100) / 100 = 2.75

For negative odds, we ignore the minus symbol and use the following formula.

(Moneyline Odds + 100) / Moneyline Odds = Decimal Odds
Example: Converting -110
(110 + 100) / 110 = 1.909
To Fractional

When converting from the moneyline format into the fractional format, the calculations again depend on whether the odds are positive or negative. To convert positive odds, you simply create a fraction by putting the relevant number over 100 and then simplifying the fraction if possible.

Example: Converting +300
300/100 is simplified to 3/1

To convert negative odds, you create a fraction by putting 100 over the relevant number (ignoring the negative sign). Again, you then need to simplify the fraction if possible.

Example: Converting -110
100/110 is simplified to 10/11

Converting Decimal Odds

To Moneyline

The method required to convert the decimal format over to the moneyline format is dependent on whether the odds are greater than 2.0 or not. We'll look at how to convert odds of 2.0 or less first. To start with, you have to carry out the following calculation.

100 / (Decimal Odds - 1)

After doing this calculation, the odds are rounded and a negative sign must be added.

Example: Converting 1.95
100 / (1.95 - 1) = 105.25
Rounded & negative sign added = -105

To convert odds of greater than 2.00, you must start with the following calculation.

(Decimal Odds - 1) x 100

You then add a positive sign to the result, as shown in this example.

Example: Converting 2.45
(2.45 - 1) x 100 = 145
Positive sign added = +145
To Fractional

The first step in converting from decimal to fractional format is to create a fraction by using the formula.

(Decimal Odds - 1) / 1

This will often create a fraction that includes a decimal, which isn't a proper fraction. To overcome this, the next step is to multiply both sides of the fraction by 100. Finally, the fraction needs to be simplified. The following example illustrates this better than any written explanation can.

Example: Converting 1.45
(1.45 - 1) / 1 = 0.45/1
Multiply both sides by 100 = 45/100
Simplified = 9/20

Converting Fractional Odds

Before we get into the math involved here, you need to understand the terms numerator and denominator. In this context, the numerator is the first number in the fraction and the denominator is the second number in the fraction. With odds of 2/1, for example, 2 is the numerator and 1 is the denominator.

To Moneyline

There are two methods needed for converting from the fractional to the moneyline format. The first is for when the numerator is greater than the denominator. The following formula needs to be used in the beginning.

(Fractional Odds) x 100

A positive sign then needs to be added to create the moneyline odds, as per the following example.

Example: Converting 6/4
(6 / 4) x 100 = 150
Positive sign added = +150

The second method is for when the denominator is larger than the numerator. In these cases, the following formula needs to be used.

100 / (Fractional Odds)

A positive sign then needs to be added to create the correct moneyline odds. This is illustrated in the following example.

Example: Converting 2/5
100 / (2 / 5) = 250
Negative sign added = -250
To Decimal

Converting odds from the fractional format to the decimal format is relatively simple and it requires just the following formula.

(Fractional Odds) + 1
Example: Converting 11/10
(11 / 10) + 1 = 1.10

Implied Probability Explained

Implied probability in relation to sports betting is basically the implication of the odds as it relates to the chances of an outcome happening. We'll cover this in more detail shortly, but first let's look at how to calculate it. It's easiest to determine implied probability from odds in the decimal format, using the following simple formula.

1 / Decimal Odds
Example: Converting 2.50
1 / 2.50 = 0.4

What this example shows us is that the implied probability of 2.50 odds is 0.40 (or 40% if expressed as a percentage). This means that odds of 2.50 on any possible outcome imply that the chance of that outcome happening is roughly 40%. So if, for example, a tennis player is at 2.50 to win an upcoming match, the implication is that he has a 40% chance of actually winning that match.

Recommended Reading

You can read more about implied probability in this article on probability in sports betting. The article also covers expected value, which is a related topic that you should definitely learn about if you want to be a successful bettor.

Understanding Vig

When looking at the odds set by bookmakers, it's important to recognize that implied probability is rarely an entirely accurate reflection of the real chances of a wager winning. This is because bookmakers always try to set the odds at levels that are lower than they actually should be in relation to real probability. If their view was that a soccer team had a 60% chance of winning a match, for example, they wouldn't offer odds that exactly reflected that chance. Their odds would be lower, as this is how they make money successfully.

By reducing the odds relative to the probability of an outcome happening, bookmakers effectively charge a commission for every wager they take. This commission is known as vig, which is short for vigorish. It can also be referred to as the overround or juice. It's similar in some respects to the house edge in casino games and it's basically what gives the bookmakers an advantage over their customers.

What sets the bookmakers' advantage apart from the casinos' advantage is that, unlike the house edge, it can be overcome. In order to overcome it, though, you first need to understand exactly how vig works and the effect it has in sports betting. You should visit our page on the subject of how bookmakers make money, as this is all about the methods that bookmakers use to ensure they are profitable. Charging vig is one of these methods that we explain thoroughly.

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