# What Are Expected Goals (xG)?

## What is xG?

Put simply, Expected Goals (xG) is a metric designed to measure the probability of a shot resulting in a goal.

An xG model uses historical information from thousands of shots with similar characteristics to estimate the likelihood of a goal on a scale between 0 and 1.

For example, a shot with an xG value of 0.2 is one that we would generally expect to be converted twice in every 10 attempts.

But that's just the start of it. Read on for a guide to understanding one of the most common advanced metrics in soccer.

## What have xG models taught us?

Many of the things we have learned from xG models are, to a degree, intuitive. Even the most casual supporter could tell you that a shot from inside the six-yard box has a greater chance of producing a goal than a shot from 30 metres out. But what an Expected Goals model provides is a statistical framework to systematically evaluate the value of each and every shot, and determine how much more likely one is to result in a goal than the other.

#### Central Shots Are Best

Shots from the central part of the penalty area are more valuable than those from tighter angles.

From the same distance, foot shots are more likely to result in goals than headed shots.

#### Crosses Are Hard

In general, crosses are more difficult to convert than ground passes, throughballs and shots after dribbles.

#### Shot Quality is Key

Given large enough sample sizes, it is possible to identify certain players who stand out for their finishing ability, but the large majority of players are close to average. In general terms, what differentiates good forwards isn't so much finishing chances at an above-average rate but generating shots from valuable locations.

## How can xG be used?

#### .cls-1 {fill: none;stroke: #8e8e8e} Team Analysis

xG can be used to get a better idea of underlying team quality beyond current results, highlighting teams who are over or under-performing their expected numbers and whose results may soon begin to change.

#### .cls-1 {fill: none;stroke: #8e8e8e} Player Analysis

Expected Goals totals can be used to determine when a player might be in the midst of a hot or cold streak in front of goal, while looking at average shot quality (xG/shot) can highlight players taking good or bad shots.

#### .cls-1 {fill: none;stroke: #8e8e8e} Head Coach Scouting

xG models provide an objective measure of underlying team performance that can be used to highlight interesting coaches who are producing effective football.

#### .cls-1 {fill: none;stroke: #8e8e8e} Predictive Modelling

Expected Goals models are utilised by both bookmakers and professional gamblers as a cornerstone of predictive modelling around future results.

## What is Post-Shot xG?

Post-Shot xG (PSxG) is calculated after a shot has been taken and generally considers shot placement, and if the model includes it, goalkeeper positioning in assigning a value between 0 (off-target) and 1 to every shot.

Traditionally, PSxG's primary utility has been in assessing goalkeeper shot-stopping ability, although newer models that include extra factors like shot velocity could provide further insight into finishing ability.

## StatsBomb xG

StatsBomb's Expected Goals (xG) model uses more contextual events and better quality data than any other provider to accurately measure the quality of chances.