The Sportsbook Margin: What is it and How to Calculate

Sportsbook margins (juice/vig) are the guaranteed earnings, a certain percentage from each bet, which betting sites take as profit. The size of the margin directly affects the value of the odds on each competition: the lower it is, the more profitable the odds for each bettor. Sportsbook's margins are not advertised, and therefore in order to assess the percent for each competiton, you can learn to calculate it yourself.


The margins in betting can be explained with just an ordinary coin. As we know, the probability of it landing on heads or tails is the same at 50 percent. And if the sportsbook took bets on this event, it should give an equivalent factor of +100 for both outcomes. 

You bet on heads, your friend on tails, and in either of the outcomes all the money delivered will be returned to the players since someone will win. But for the sportsbook this is unprofitable. It, therefore, makes its commission, by allowing you to bet on 50/50 events but not with a factor of +100, but, say, -110, which corresponds to a margin of 4.7 percent.

With two players betting on opposite sides of 100 conditional units, each sportsbook will return to circulation -110 and always take away nine conditional units. In the context of these events, you can never make a profit at a distance only because of the margin factor. However, in other events where you show a predictive talent for making bets, the margin becomes just an additional barrier.

With a margin of four percent, you now have to be four percent more accurate over time, in order to not lose money. The margin is a barrier from the start that needs to be overcome in order to make a profit, and the size of this barrier varies depending on the sportsbook, the popularity of the event and the sport and individual lines. It is most convenient to calculate the margin as a percentage.

How to Calculate the Margin as a Percentage?

Calculating the margin as a percentage does not have to be a difficult process. The two most common instances to calculate margins are events with two or three options to choose from. 

The calculation formula for outcomes with two options:

Margin = 1 - 1 / (Probability 1 + Probability 2), where Probability 1 = 1 / Odds 1, and Probability 2 = 1 / Odds 2.

For example, let’s take one of the most popular sports for betting- tennis. Novak Djokovic and Juan Martin Del Potro met in the final of the US Open 2018. The sportsbook took bets on Djokovic's victory with odds of 1.45, del Potro - 2.84.

Margin = 1 - 1 / (1 / 1.45 + 1 / 2.84) = 4%.

Thus, the sportsbook's margin for the main outcomes of the US Open final was four percent.

Calculating the formula for bets with three outcomes:

Margin = 1 - 1 / (Probability 1 + Probability 2 + Probability 3), where Probability 1 = 1 / Odds 1, Probability 2 = 1 / Odds 2, Probability 3 = 1 / Odds 3.

Now consider the Champions League match between CSKA and Real Madrid. The sportsbook estimated the victory for CSKA by a factor of 7.15 (+615), a draw at 4.05 (+305), and the success of Real Madrid could be played for 1.58 (-1.72) . We can calculate the margin based on the proposed odds:

Margin = 1 - 1 /(1 / 7.15 + 1 / 4.05 + 1 / 1.58) = 1.93%

The Champions League is one of the world’s leading betting tournaments, it is an extremely reliable competition, so the sportsbook limited himself to a low margin of 2.57 percent for a group stage match. 

Tips for Beginners about Betting Margins

Do not lose your vigilance from the examples presented, it may seem that the margin in football is lower than in tennis, but that is not exactly true: in this instance, rather, it is simply a difference in the approach of individual sportsbooks- who have their own priorities.

Indeed, each sportsbook has its own tactics to attract players, and the size of the margin is just one of these tools. The comfort of the game can be influenced by a variety of factors: the number of offers and sports, the convenience of I/O, bonus shares, betting limits and so on. 

When choosing a profitable sportsbook, you should always be on the lookout. On the same sports betting site you can find main outcomes with a 3% margin and in the same event, but on different bets (say, over/under on corners), you will instead face a margin above 7%.

The strong value of the margin depends on the popularity of the tournament and the sport in a single sportsbook. The advantageous odds for the Champions League are not a guarantee that the same sportsbook will make a generous offer for baseball or cricket.

All offers should be checked individually so you can choose a sportsbook suitable for your style of play. Using the formula to calculate margins, you can protect yourself from falling into a notoriously losing situation and choose profitable odds to your liking. 

The main thing is to treat the margin without fanaticism- for example, in the vegetable market you buy not only from the seller with the lowest price but also where the products are fresh, there are more choices or if the seller is just pleasant to talk to as a person.

When choosing a sportsbook, you consider a combination of factors, because you need to play responsibly and have a good time while doing it. At Legalbet we will also use our own unique formula for calculating sportsbook margins.

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