How long do trailers and commercials last before the actual movie starts?

Right now, after the lights go down, Cinemark shows 15 minutes worth of trailers before the actual movie begins while Regal’s trailer block runs 15 to 20 minutes, according to the news report.

https://entertainment.slashdot.org/story/19/10/01/1634225/movie-theaters-latest-gamble-ads-mixed-in-with-trailers

* Personal experiences:
Star Wars – The Rise of Skywalker – at the Regal cinema on Hampden. Ticket was for 6:30 and the movie started at 7:00.

The Black Phone –  at the Regal cinema on Hampden. Ticket for 5:30, movie started 5:54.

Everything Everywhere All at Once – Landmark Chez Artiste on Colorado. Ticket for 4:00, movie started at 4:15. (Landmark theaters seem have the shortest wait time.)