Determining stoppage time in a soccer match is one of the referee’s many jobs, and the process is simpler than you might expect.

The clock is always running in a soccer game, even when there are stoppages of play. Instead of pausing the clock for every single substitution, injury, or free kick, the time is simply added to the end of the half.

Unlike extra time, which is a set amount of time that extends a soccer match, stoppage time is much less predictable. In fact, the additional minutes tacked on at the end of each half is all down to the referee’s discretion.

There is a system in place, though, that accurately determines just how much stoppage time is necessary before the referee blows the final whistle.

The official determines stoppage time in soccer by keeping track of every pause in play throughout the half, from fouls to goal-scoring celebrations. Then, they calculate how much added time is needed to account for all the stoppages.

Once they have the correct amount of time, they communicate it to the fourth official, who will hold up the number on the same electronic board used for substitutions. Typically, at the end of the second half, the board will read anywhere from three to five minutes.

If there were prolonged stoppages in play, though, for a lengthy VAR review or a critical injury, the stoppage time will be much higher. Technically, there is no maximum stoppage time allowed in a professional soccer game, so players could be on the pitch for an extra 10 minutes if needed.

There is also no guarantee that the half or the game will end as soon as stoppage time finishes. More delays during the additional minutes, including time wasting or substitutions, can extend stoppage time.

The teams will not leave the pitch until the referee blows the final whistle after they deem the stoppage time officially over.