Different Odds Formats
As you can see, the fundamental principle behind odds is really quite straightforward. Things are slightly complicated by the fact that there are three different formats of odds as follows:
Chances are, at some point, you'll encounter each of these formats. For this reason, it pays to be familiar with each one. They all work in essentially the same way--basically just different ways of expressing the actual odds for any particular wager.
Moneyline or American Odds
Moneyline odds are also known as American odds, and this is the format most commonly used in the United States. They can be displayed as either a positive or a negative number. A positive number expresses how much a correct wager of $100 would win, while a negative number expresses how much you would need to stake in order to win $100. If you saw odds of +150, you would know that a $100 bet could return $150 in winnings, plus the initial stake of $100. If you saw -150, you would know you need to stake $150 to return $100 in winnings, plus the initial stake of $150. An even money wager (where you stand to win an amount equal to your stake) is expressed as +100.
Decimal odds used to be associated mostly with mainland Europe, Canada, and Australia. However, they have now largely become the standard at most online bookmakers with the exception of some US betting sites. This is because they are the most straightforward of the three formats and are expressed simply as a single positive number, typically to two decimal places. The number shows how much the total payout will be, including the original stake per unit staked. For example, a winning bet at 1.5 would return a total of $1.50 for every $1 staked. A winning bet at 2.25 would return a total of $2.25 for every $1 staked. An even money bet is expressed as 2.00.
Fractional odds are the traditional format used in the United Kingdom, although decimal odds are slowly taking over. Calculating potential profits and payouts with this format can be a little tricky, certainly to start with, but the basic principle isn't as complicated as it might seem. As with moneyline odds, fractional odds show how much potential profit you can make. To calculate the total potential payout, you have to add your original stake.
As the name suggests, these odds are displayed as a fraction. A simple example is 3/1, which is said as "three to one". 5/1 is said as "five to one", and so on. With 3/1, you can win three units for every one unit staked, and with 5/1 you can win five units for every one unit staked. 1/1 is even money, so you can win one unit for every unit staked. As you can see, this is quite straightforward so far.
Things get slightly more complicated, because this format also includes examples such as 6/4, 11/10, and 5/2. The math involved is thus not always so simple. With 6/4, you can win six units for every four units staked, which is equal to 1.5 units per unit staked. With 11/10, you can win eleven units for every ten units staked, or 1.1 units per unit staked.
Whenever the first number is larger than the second, this is said to be "odds against." These are basically the equivalent of positive moneyline odds in that the potential profit is greater than the amount staked. Things get even more complicated as there are also "odds on" odds. These are the equivalent of negative moneyline odds in that the potential profit is less than the amount staked.
An example of odds on is 1/4 is said as "four to one on". 4/7 is "seven to four on", and so on. With 1/4, you can win one unit for every four units staked, and with 4/7 you can win four units for every seven units staked.