If a goalie has been in net for 977 minutes, has allowed 18 goals in that time, and regulation time for the league they play in is 90 minutes per game:
18 goals against times 90 minute game length is 1,620.
1,620 divided by 977 minutes played is 1.658
Therefore, the goalie’s Goals Against Average (GAA) is is1.658
What is Goals Against Average?
It is considered one statics among a number of other ones, including win/loss ratio and save percentage that are used to help measure a goalie’s capability.
What counts as a “Goal Against”?
If the goalie is not on the field of play at the time when the goals happens, a goal against the team does not cont against the goalie’s GAA.
Rules for what qualifies as a goal can be found in the FIFA laws of the game (other leagues with alternative rules may have different scoring regulations).
What counts as a “Minute Played”?
What is “Game Length”?
FIFA level matches have a game length of 90 minutes (2 halves of 45 minutes). Recreational leagues may have shorter halves.