What is the regulation length of an NHL game, including three periods?

The regulation length of an NHL game is 60 minutes, divided into three 20-minute periods.

NHL game clocks use stop time, so the clock stops whenever play is whistled dead, a goal is scored, or another stoppage occurs. Two intermissions separate the periods, meaning the total time inside an arena is much longer than the 60 minutes of actual regulation play—often around two and a half hours once stoppages and intermissions are included.

The NHL changed from two 30-minute periods to three 20-minute periods for the 1910–11 season. That three-period structure remains one of the sport’s defining features.

Regulation does not include overtime. In the regular season, a tied game after the three periods proceeds to a five-minute, three-on-three overtime and, if necessary, a shootout. Stanley Cup playoff games use successive 20-minute sudden-death overtime periods instead.