How to Calculate and Use the xG (Expected Goals) Metric?

An interesting question landed on our “Ask the Experts” panel. Our visitor with the username Gerald asks the following:

“What is the best way to calculate expected goals, and how best can it be used?”

First, let’s see what exactly “expected goals” are. xG, or Expected Goals, is a special metric for football (and ice hockey) matches to measure the probability of a player’s shot becoming a goal. A special formula calculates the probability of each shot in a game to be a goal. The scale ranges between 0 and 1. Using the xG stats, you can understand deeper insights into the team and the players and how they perform. Nowadays, the Expected Goals metric is used not only in pre-match analysis using historical data but also in live matches.

For example, a show with an xG rate of 0.5 is expected to score a goal five times from ten attempts.

How to Calculate the Expected Goals in a Football Match?

There are various xG models, and each one of them has its own characteristics. However, certain factors are traditionally used to determine the xG metric:

Distance of the shot to the goal
Angle to goal
Type of assists or previous movement (set-piece, cross, dribble or other)
The body part from which the shot is taken
The number of defenders that are around

The xG models are using complex formulas to calculate the xG rate based on the characteristics mentioned above. The result from the calculation provides the probability of the shot resulting in a goal.

Actually, in my opinion, there is no need for us, the bettors, to calculate the xG metrics ourselves. There are a lot of statistical websites and apps that provide this info. Also, many of the betting sites provide the xG metric in live games.

At the end of the day, expected goals are just metrics and are not 100% right all the time. There are many examples of football matches where a team’s expected goals are more than 1, but the team doesn’t actually score a goal. However, these metrics are collected in a database that can help you make future match predictions and determine if the team has a lot of chances in a game but doesn’t convert them.

How to use the xG metric?

There are various ways to use the Expected Goals metric, and the most important of them features:

Team Analysis
Player Analysis

Using the xG value, you can evaluate players’ and teams’ performances. It is known that if a team usually provides a high xG ratio but fails to score the expected number of goals, sooner or later this will change, and they will start converting their chances.

If you analyse a football match and see the xG ratios of both teams, and, for example, they produce xG more than 1.00 historically, it is likely that they will manage to score at least one goal each in the upcoming match. However, I recommend not only sticking to analysing the xG ratios. There are various factors that can affect the game, like recent news, missing players, h2h records and more.