First, there are three types of odds: Decimal, american, fractional.
If this sounds a bit like a math class, that’s because in a way it is. Being good at math in betting has the potential to pay off more than simply getting a good grade. These three types usually represent the odds from European, American and English view respectively. Each type can be converted to another and do not affect the calculation of the actual payout. This is important because it allows you to convert the probability, expressed in percent, of any betting event.
The betting example we will be using throughout this article will be the betting line on the 2018 Super Bowl, which has the New England Patriots favored to repeat as champions.
Also known as Continental, European, and Digital odds, this type is the most commonly found in the countries of: the main continent of Europe (France, Spain, Italy, etc.), Canada, Australia, and New Zealand. This is usually considered the easiest of the three systems to understand, though may not be the best to use. It is easier to see both the favorites and underdogs at a glance.
The decimal number represents your total winnings including your wager. Compared to the other types, the decimal system is very straightforward math:
Your total return = amount wagered x Decimal odds
If you wager $100 for the New England Patriots to repeat, and the decimal odd value for the line is 4.5, the total potential return is $4500 (4.5 x 100). But your actual winnings (profit) would be $4500 - $100, the original amount wagered or $4400.
Also known as Moneyline and US odds, this type is used primarily in the United States. The favorite is indicated by a minus sign (-) in front of the betting line. A plus sign (+) is used to show the underdog for the event. The American system indicates the amount you will win, not including your original wager.
Your total return for the favorite winning = 100 x (American odds / amount wagered)
Your total return for the underdog winning = American odds x (American odds / amount wagered)
If you wager $450 for the New England Patriots to win Super Bowl 52 as the favorite and the American odds value for the line is -450, the total potential return is $100 for every $450 wagered.
If you wager $100 for the underdog to win Super Bowl 52, and the American odds value for the line is +450, the total potential return is $450. You receive $450 for every $100 wagered.
Also known as Traditional, UK, or British odds, this type is heavily favored for use by bookmakers around the world. The symbol used to indicate the odds is either a slash (/) or a dash (-). For example, a common way to express the betting line is to say the odds are “10 to one.” The Fractional Type will show this as either 6/1 or 6-1. For every dollar you wager on the right side of the symbol you will get back the number of dollars on the left side of the symbol.
If you place a $100 wager on the New England Patriots to win Super Bowl 52 at 450/1 (or 450-1) you would get back $45,000 if they won (100 x 450).
Converting From One System To Another
From American to Decimal
To place a wager on the underdog, the calculation is - Decimal odds = (US odds/100) +1
To place a wager on the favorite, the calculation is - Decimal odds = (100/US odds) + 1
From American to Fractional
To place a wager on the underdog, use the formula – Fractional Odds = (moneyline/100)
To place a wager on the underdog, use the formula – Fractional Odds = (100/moneyline)
From Decimal to American
If the Decimal Value is greater than 2.00 the calculation is - US odds = (Decimal – 1) x 100
If the Decimal Value is less than 2.00, the calculation is - US odds = (-100)/ (Decimal -1)
From Decimal to Fractional
Fractional Value = (decimal value -1) which is then converted into a fraction
From Fractional to Decimal
Decimal Value = (convert the fractional value into a decimal, then add 1.00
From Fractional to American
If the Fractional Value is 1/1 or higher
American Value = Moneyline = (fraction value)*100
If the Fractional Value is less than 1/1
American Value = Moneyline = -100/ (fraction value)
Which is the Best System to Use?
There is a reason the Fractional Type is preferred by bettors from virtually every country. The conversions are much simpler and you can calculate your winnings without using a calculator. The American Type is the most difficult because it requires you not to get confused between the underdog (+) and favorite (-) which in itself seems contradictory. But in any event, it is necessary for you to know how to use and convert all three betting types.