In a nutshell
Expected Goals (xG) is a statistical metric which assesses every chance created during a football match, assigning a probability or likelihood of each individual chance being scored. The higher the xG (1.0 being the maximum), the more likely the opportunity of being taken. So if the xG is 0.3, the chance should be scored 30% of the time. A penalty has an xG between 0.76 and 0.80 depending on the domestic league.
How does it work?
Expected Goals, often abbreviated to 'xG', is a metric used in football just like 'shots' or 'tackles', that quantifies the quality of any given scoring opportunity and attributes the chance a probability of it being scored.
The higher the probability, the better the chance.
Many football fans will already know that a player has a better chance of scoring with a shot from the edge of the six-yard box than a shot from 30+ yards, but on the stats sheet after a game, these two shots are viewed equally in the 'shots' column.
Expected Goals would attribute 0.40 xG (40%) to the shot from the six-yard line, and 0.02 (2%) to the shot from distance, making it clear to see that one chance was much better than another.
All of the xG from all of the shots across a game are tallied up and, along with the actual result (3-1 for example) we can generate an xG result (1.6 - 2.3 for example), which would give a fairer representation of the quality of chances a team creates over the course of the game, not just the quantity.
In this example game, the losing team created the better of the chances, while the winning team were slightly fortunate to score three from their opportunities.
Both of these facts will be taken into consideration over the long run, and xG can help build a much clearer picture of teams going forward than just the 'actual results', providing a much more descriptive look over a long period of time, helping to give a better insight into future performances.
How likely is it that teams are going to be able to repeat their current form? Is the team over-performing or under-performing? xG can help answer those tricky questions.
How xG can help your betting...
Expected Goals is a much more useful tool to measure a team's future performances rather than just looking at their results or the number of shots they had.
Taking a team's underlying xG process (average xG ratings in attack and defence) can give a much more informative view of what to expect from a team in any given game, so value can sometimes be found when there is a reaction to a few good recent results that were perhaps undeserved.
A great example of this from last season was when Wolves played Manchester United towards the end of the campaign.
Ahead of the game in April, Wolves were ranked as the fifth best team according to expected goals, while Manchester United were running very hot under Ole Gunnar Solskjær at the time, being fortunate to win as many matches as they did according to xG.
Betfair had the game priced up with Manchester United as 21/20 favourites to win the game, but the Infogol model, using expected goals, had Wolves the favourites to get the win (40%, around 6/4).
The game ended in a 2-1 win for Wolves, with xG helping us to find an edge, and in this case, a big edge.
What is Infogol?
Infogol is a revolutionary football product, which harnesses Opta data to power an xG model, which can both analyse results and predict outcomes of forthcoming matches.
The free to download Infogol App and website - infogol.net - uses Expected Goals data to generate the best value betting tips across the big five European leagues (Premier League, La Liga, Serie A, Bundesliga and Ligue 1) as well as the Championship and Brazil's Serie A.
As well as being a betting companion, the Infogol model offers a new and unique in-play experience, with live in-play xG shot maps available, a Half Time Team Talk with a first half summary and recommended bet, Forecast tables and Actual vs Expected tables so you can see where your team should be in the league based on xG.
Pre-match probabilities and Analyst Verdicts are available for all matches, in a bid to help users find the best value possible when looking to place a bet, and the blog section is full of detailed analysis, match previews and reviews - all powered by expected goals.