Traditionally, screenplays are printed on 8 1/2″ x 11″ white 3-hole punched paper. The number of the pages appears in the upper right hand corner (in the header), but there is no page number printed on the first page. The font style used is Courier and font size is 12. The top as well as the bottom margins are between 0.5″ and 1″. The margin on the left side is between 1.2″ and 1.6″, and on the right is between 0.5″ and 1″. There already exists script writing software that is pre-programmed with all these rules.
Traditionally, the average screenplay for a feature film is between 95 and 125 pages long. In Hollywood, today’s scripts generally do not run longer than 114 pages. Scripts for comedies are typically shorter, while drama scripts are longer. Naturally, there are variations. This means you could write an action-packed motion picture where your description requires only 10 seconds of reading, but will require 45 seconds of film time. Writing would depend on the style of the writer.
Scripts that have 125 pages are considered long. Length is a very important element of the script. It does not matter if you have written a very beautiful screenplay; if it is too long producers may refuse to read it.
If you think your script is too long and you want to shorten it, put in mind that if a scene can be taken off and the story persists to flow, that scene is not necessary. Always remember that every scene should be an essential component of the path to the climax.