According to an official listing at the BBFC
(British Board of Film Clasification) the official runtime of Star Wars: The last Jedi will be 151m 38s. That's close to 2+1/2 hrs of Star Wars. It also dethrones 2002's Star Wars: Attack of the Clones which was only 142 minutes.
Don't fill up on beverages, you might miss the good part!