The late John Pytlak often helped forum members with such questions, but it has been years since his passing. You would find it helpful to use the search feature and change the search parameter to "Any Date". All your questions on cinema design have probably been answered multiple times.
Here is a quote from John Pytlak written in 2003 to answer your question:
As a guideline, remember your screen should ideally have an aspect ratio of 2.4:1 (fill the screen with a "scope" picture). So a screen would be 5x12 feet, 10x24 feet, or like proportions.
Standard SMPTE 196M specifies the preferred viewing distance to be between 2 and 4 times the screen height. So MOST of your seats should be in that range (e.g., for a 10x24 foot screen, between 20 and 40 feet from the screen). Of course you may want to up seat count by having some "booker seats" much closer to the screen, and some people like to sit further from the screen, so seats up to about 5 screen heights are used. But much farther than 5 screen heights, you might as well be watching television.