An NBA basketball game has four quarters of 12 minutes each. That produces 48 minutes of scheduled playing time before overtime is added.
The quarter structure separates the game into four equal periods, with a halftime break after the second quarter and shorter breaks between the other quarters. The clock stops during many dead-ball situations, so an NBA game takes considerably longer than 48 minutes to watch in real time.
The 48-minute format is an NBA convention rather than a universal basketball rule. International games played under FIBA rules use four 10-minute quarters, while college basketball in the United States traditionally uses two 20-minute halves. This difference is one of the most common sources of incorrect answers.
If the score is tied after the fourth quarter, the game continues into five-minute overtime periods until one team leads at the end of an overtime period. Overtime does not change the standard length of the four regulation quarters; it simply adds extra playing time when necessary.