Betting Guide: Probability versus Betting Odds and Odds Calculator

The basis of any bet, either with your friend or with a bookmaker at the betting outlet, is the probability. Consciously or subconsciously you will always put a probability to the predicted outcome. In the betting industry, the probability of any outcome is mirrored in betting odds.

Probability versus Betting OddsCalculator
Fair Betting Odds & MarginCalculator

Probability versus Betting Odds

Try to imagine that there will be a Manchester City against Cardiff match next Saturday. You feel that there is a 95% probability that City will win. 95% probability means that fair odds should be 1.05. In case that bookmaker is offering higher odds, e.g. 1.07, it means that he thinks that probability of City winning the match is just 93.46%. In that case, you should take advantage of your feeling of probability and bet on the City. (Note: I do not recommend to bet such lower odds in general)

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The probability is the key to the betting decision process. The successful tipsters are trying to bet when they see the probability of the outcome higher than the bookmaker. That is the simple first rule you should stick to.

The Probability to Betting Odds Calculator and Betting Odds to Probability Calculator


Fair Betting Odds and Margin of Bookmakers

Professional tipsters always start the decision process on the bet with allocating probabilities to all possible outcomes of the match. Imagine, that Real Madrid is playing at home with Barcelona. You see the probability of Real Madrid win, Barcelona win and draw at the same level 33.33%. In other words, you see the same chance of any possible outcome. (Note: The sum of probabilities for all outcomes has to be 100% because one and only one of the outcomes will definitely happen.)

In our imaginary scenario, the betting odds for the above-mentioned match should be 3.0 – 3.0 – 3.0.  However, that would happen just in the ideal world. In the real world, you will probably get odds 2.9 – 2.9 – 2.9. That would mean that bookmaker see the probability of every outcome at 34.48% and the sum of probabilities is 103.44%. 3.44% is the margin of the bookmaker. In case that bookmaker will take the same amount of bets at every possible outcome, he will earn 3.44% of the sum bet on the match, no matter what the result will be.

The margins of bookmakers differ depending on the sport and the exact match. Generally, the bigger favorite in the match is, the higher-margin will be included in odds.

I do not see the margin as absolutely unfair (of course it depends on how high it is), as bookmakers need to cover their costs and provide also a lot of additional services (statistics, live scores, etc.). The fair odds are available just in case you are making a bet with your friend. Betting exchanges also tend to provide fair odds as they are ruled by supply and demand. But do not forget, that you will pay a commission from net winnings to the exchange, that impact the net odds you are able to realize.

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The Probability to Betting Odds Calculator

Betting Odds to Probability and Bookmaker’s Margin Calculator


This blog post was written by Mr. Kostrava. Simon Kostrava is a professional tipster and author of the popular book The Betting Industry: Who Makes the Most Money and How?. He also runs two very successful and profitable betting portfolios: Tennis Only and Soccer Soda – Soccer Only.


Want to learn more about the betting industry? Looking for advice on how to be successful tipster in the long term? Read the book revealing betting industry secrets:

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