So, how long is James Cameron's 'Avatar'?

James Cameron's sci-fi epic "Avatar" will open in theaters and IMAX everywhere Dec. 18, 2009, but until now, on one really knew the film's final running time. Now the answer is here: 150 minutes.

Twentieth Century Fox's Bruce Snyder told the Hollywood Reporter the movie would run 2.5 hours. With all credits added, it may even run for a total of 156 minutes, but definitely not longer.

The reason why "Avatar" won't run any longer is the inability of some IMAX theaters to play a movie longer than 170 minutes. "Avatar" will play in 3D at around 2,500 locations (180 IMAX) and 2D at 1,500 locations.