How long is a movie? [closed]

It's somewhat a matter of opinion. However, the Academy of Motion Picture Arts and Sciences defines a short movie as having a running time of 40 minutes or less (pdf).

By their definition a "full" feature length movie has to be more than 40 minutes.

I am not aware of any upper limit, there are movies such as Andy Warhol's Empire (1965) which is over 8 hours long and was shown in movie theaters. If that seems too much like an art installation rather than a feature film, there are a number of mainstream movies that are far longer than most made today:

• Gone with the Wind (3hr 58 minutes)
• Once Upon a Time in America (3hr 49 minutes)
• Lawrence of Arabia (3hr 36 minutes)