Here’s a concise write-up regarding the runtime of High School Musical 3: Senior Year :

has a runtime of approximately 112 minutes (1 hour and 52 minutes).

This makes it the longest film in the original High School Musical trilogy. The extended length accommodates the movie's transition to a theatrical release (unlike the first two TV movies), allowing for more elaborate musical sequences, a larger scale of choreography, and deeper emotional closure for the characters as they face graduation and separation.