Here's the most simplistic but true statement I can possibly make about sports betting - understanding sports odds is a pretty important part of sports betting. You can be the best handicapper in the world, and you can pick winners with shocking regularity, but if you don't understand odds then you can't know if a bet is worth making, and you probably won't be a winner in the end. Fortunately, understanding sports odds isn't that tough once you figure it all out.
Before we look at the details of things there is one thing to keep in mind - your job as a sports bettor is to determine what you think the likelihood of something happening is and then to compare it to the odds of that event occurring. If the posted odds are better than your anticipated likelihood then you have a bet worth making, but if the odds, or the potential return on the bet, is less than the chances you give the bet of being successful then it is not worthwhile. Novice or unsuccessful bettors think that sports betting is all about picking winners, but that is only a small part of success.
There are a number of different ways that odds can be presented, but they all come down to the same thing. Sports books assign what they think is a fair price for a particular outcome. By fair price I mean that the books try to set a price that is attractive to bettors so that they will bet on it, but not so attractive that they will get too many bets and risk losing money. Books will adjust the odds once they have been set if they are attracting too much or too little action.
Sports odds can be presented in a number of different ways, but they all represent the same thing in one way or another - the amount you will win if you make a bet and are correct. They express them in different ways, but that's the meaning.
Fractional odds - These aren't the most common in sports betting, but they are the easiest to understand so we will start here. They are used in horse racing, so if you are familiar with betting on the ponies then you know fractional odds. Not surprisingly, they are expressed as a fraction. For example, odds of 4/1 mean that you would win four dollars if you bet one dollar and were correct. The odds can be less than even, too. Odds of 1/4 would mean that you would have to bet four dollars to win one dollar. With fractional odds it is also quite simple to figure out if a bet makes sense. If the odds are 4/1 and you think that something is likely to happen once in three tries then it is a very profitable bet. On the other hand, if it were likely to happen once every five tries then you would lose money in the long term if you bet it at 4/1.
Decimal odds - These aren't used in the United States very often, but they are seen in Canada, Europe and Australia. They can also be the most confusing at first. The easiest way to understand them is to start with fractional odds. To make a conversion you take the fraction, turn it into a decimal, and add one. That means that 4/1 fractional odds would convert to decimal odds of five, and 1/4 odds would become 1.25.
Money line odds - These are by far the most common form of odds in North America for sports betting. They are expressed as numbers greater than 100, and they can be either a positive or negative number. Each one is a little bit different.
When a money line is a positive number then the odds are the amount you would win if you were to bet $100 and were correct. For example, a money line of +200 would mean that you would make a profit of $200 if you bet $100 and were correct. That's also equivalent to fractional odds of 2/1 and decimal odds of 3.
A negative money line represents the amount that you would have to bet to win $100 if you were correct. For example, a -200 money line means you would win $100 if you bet $200 and won. It is also equivalent to fractional odds of 1/2 and decimal odds of 1.5.