betting odds

iGamingNuts: Betting odds – everything you should know

About the author:

Lukasz Nowicki is an experienced analyst in the gambling industry. For over 10 years has been preparing articles about betting products and analysis of betting companies. Since 2016 has been one of the key publishers at, owner of top polish affiliate site


The odds are one of the key factors related to sports betting. Together with the stake for which the bet is placed, they are decisive in determining our possible win. Is it worth finding out how they are calculated? Of course! Betting odds are a reflection of the chances for which the bookmaker estimates the occurrence of a given bet, and this may turn out to be useful in searching for events to bet on. Let’s learn more about odds in sports betting.

Who sets the betting odds?

The people who calculate the odds for bookmakers are the so-called oddsmakers. They are professional sports experts and analysts who, using their own knowledge and special analytical tools, are able to calculate the chances of a given result as effectively as possible. What’s interesting, most of the oddsmakers were usually professional punters in the past, very often very successful ones.

Analyses applied to determine the odds usually include a large amount of data, such as the current form of players/teams, injuries and exclusions, head to head results, the tactical setting for a given match, etc. What’s important, oddsmakers generally have access to a larger number of variables than the usual punters, so the chances in this confrontation are usually more favourable for the bookmakers. However, the oddsmakers are human as well, and they also make mistakes from time to time. The key to success in sports betting is to take advantage of their slip ups.

Of course, nowadays human beings are assisted by algorithms which automatically adjust the value of the odds depending on how many players are betting on a given result. Monitoring the odd drops may often turn out to be a profitable strategy as well.

Betting odds – useful calculations

The odds themselves reflect the percentage chances of a given result to appear. How can we calculate them? As an example, let’s analyse the odds of Liverpool FC to win the EFL Cup game against Arsenal London.

The fractional odds on Liverpool to win at William Hill are 1/1. To calculate probabilities based on fractional odds, we use the following formula:

Probability = B / (A + B), where A is the first digit and the denominator of the fraction, and B is the second digit – the numerator.

If we take the odds of 1/1, we are able to calculate the probability as follows:

1 / (1 + 1) = 0.50

This means that Liverpool’s percentage chances of winning according to the bookmakers are 50%. Let’s look at some other examples of fractional odds probabilities:

3/1 à 1 / (3 + 1) = 0.25 – in this case the probability of this result is 25%

1/2 à 2 / (2 + 1) = 0.66 – the probability of this result is 66%.

1/4 à 4 / (4 + 1) = 0.80 – the probability of this result is 80%.

With the help of betting odds, we can also calculate our possible winnings. In this case, the calculation is even simpler – the first digit of the fractional odd is the amount you will win together with the wagered stake, which is described by the second digit.

For example:

7/1 means that for every £1 wagered you will win £7

3/1 means that for every £1 wagered you will win £3

1/2 means you will win £1 for every £2 wagered

1/4 means you will win £1 for every £4 wagered

Bookmaker margins

Interestingly, if we add up the percentage probability of results offered by any sportsbook on a given market, it will surely total more than 100%. As an example, let’s take the Premier League matchup between Manchester United and Tottenham Hotspur. The odds for the basic 1X2 market offered by one of the top British bookmakers are the following:

Manchester United (1) 17/20 à 54.05% chance

Draw (X) 11/4 à 26.66% chance

Tottenham Hotspur (2) 3/1 à 25% chance

If we add the percentages, their total will be 105.71%. What does the 5.71% surplus mean? It is the so-called bookmaker margin, i.e. the commission that the bookmaker charges for operating bets. Keep in mind that higher margins do not mean anything good, as higher commissions mean less attractive odds and therefore lower wins.

Betting odds in practice

Significant odds changes in football betting are most likely to occur when one or more important players of the team drop out from the squad. These types of odds fluctuations have recently been particularly visible during the coronavirus pandemic – the odds to win for a team whose players were infected usually increase rapidly, especially if the remaining part of the first squad was suddenly quarantined and the team is forced to play with substitute players.

Recently, this type of situation occurred in the Scottish Premier League, where three Kilmarnock players were infected. The team was scheduled to face Motherwell a few days later. The reaction of some of the bookmakers was very quick – Bet365 deleted the event from their sportsbook, and Motherwell’s odds to win at some of the bet operators began to drop. For example, at Bet-at-home these odds changed from 37/20 to 17/10 within a couple of hours, while 24 hour before the start of the game the odds for Motherwell’s win averaged at 27/25.

There are many similar examples in football. Often, even rumours of key players indisposition ahead of an important game can have a major impact on the pre-match odds. Therefore, punters with access to the best and fastest sources of information will usually make the greatest profit.

How can a punter use this knowledge?

Knowing how to set bookmaker odds may also be useful for players who use various types of betting strategies, including value betting. After all, calculating the probability of winning and estimating the value of a given bet is one of the most effective betting methods available. Therefore, it is worth familiarizing yourself with how the odds are calculated in order to increase your chances in an uneven duel with the bookmaker and to maximise your profits from sports betting.


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