Understanding xG (expected goals)
Expected goals, or xG, estimate how many goals a team "should" have scored from the chances it created.
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What xG measures
Every shot is given a value between 0 and 1: the historical probability that a shot of that kind becomes a goal. A penalty is worth roughly 0.75 xG, a long-range shot perhaps 0.03. Adding up all shots gives a team's xG for the match.
Why xG is useful
Goals are rare and partly random, so a few matches of goals can say little about how good a team really is. xG counts every chance, which makes it more stable: a team that creates 2.0 xG per match is likely to score more in future than one that creates 0.8, whatever their recent results.
What xG does not measure
- Finishing or goalkeeping quality beyond the average (some players do beat their xG over long periods).
- Chances that never became shots.
- Differences between xG models: providers calculate xG differently, so values are not perfectly comparable.
How FootIQ uses xG
FootIQ's empirical-Bayes model uses a team's xG instead of goals when the data provider has it, because it is less noisy over short periods. The analysis panel also shows recent xG form. See the methodology.