Spec Screenplay Page Properties
Screenplays are traditionally written on 8 1/2" x 11" white 3-hole punched paper. A page number appears in the upper right hand corner (in the header). No page number is printed on the first page. The type style used is the Courier 12 font. The top and bottom margins are between .5" and 1". The left margin is between 1.2" and 1.6". The right margin is between .5" and 1".
The extra inch of white space on the left of a script page allows for binding with brads, yet still imparts a feeling of vertical balance of the text on the page.
The Courier 12 font is used for timing purposes. One script page in Courier 12 roughly averages 1 minute of onscreen film time. Experienced readers can detect a long script by merely weighing the stack of paper in their hand.
Script writing software is pre-programmed with all these rules right out of the box.
The average feature screenplay, traditionally, is between 95 and 125 pages long. In Hollywood these days scripts generally don't run longer than 114 pages. Comedy scripts are typically shorter, dramas longer. There are, naturally, variations. You could be writing an action-packed film where your description takes only 10 seconds to read, but will take 45 seconds of film time. Here's an example:
Cpl. Owens sheds his pack and picks up the machine gun. He runs from doorway to doorway, dodging enemy fire while shooting back, until he reaches the church bell tower.
If you had a script full of scenes like this, you could come up with a short script in total pages... but that doesn't mean when it is filmed it would be short. By the same token, another writer could write the same scene and have it take up half a page. It just depends on the writing style of the individual writer.
125 page scripts are considered on the long side for a screenplay. Length is a very important component of the script. When you turn in a script to a producer, the very first thing s/he will do is fan through the pages and look at the last page to see how long it is. It doesn't matter if you've written the most incredible screenplay ever, if it's too long they may refuse to read it.
The Industry's aversion to long scripts is due to economic considerations. Films under two hours mean more showings per day in a theater, which means more revenue for the exhibitor, distributor, filmmaker, and possibly even you, the screenwriter.
When you realize your script is long and have to start cutting your work, keep in mind that if a scene can be removed and the story continues to work, that scene wasn't necessary. EVERY SCENE should not only move the story along to its conclusion; it should be an integral part of the path to the climax.