What is Expected Goals?
A closer look at chance quality, beyond the final score.
A closer look at chance quality, beyond the final score.
The definition
Expected goals (xG) estimates the probability that a shot becomes a goal, based on the information available to a model. A shot assigned 0.20 xG represents an estimated one-in-five scoring chance across comparable situations. Summing shot probabilities gives a team’s match xG.
How the estimate is made
Common inputs include shot location, angle, body part and the preceding action. Richer models can account for goalkeeper and defender positions. Different providers use different data and assumptions, so their xG values are not interchangeable.
Reading an example
Suppose a team takes three shots valued at 0.10, 0.20 and 0.40 xG. Its total is 0.70 xG. This is an expected goal count, not a 70% probability of scoring at least once. Assuming independent shots, that probability would instead be 1 − (0.90 × 0.80 × 0.60), or 56.8%. This example is illustrative.
What xG cannot tell you
A single match is a small sample. An xG total does not by itself describe possession control, off-ball defending, or chances that never became shots. Pre-match predicted goals are also different from retrospective shot-based xG. NinetyQuant labels its pre-match scoring rates as illustrative inputs, not observed match statistics.
Sources & further reading
Prepared by NinetyQuant. Numerical examples are illustrative. References explain general concepts and do not validate NQ’s demo forecasts.