Viewing Distance Calculator

Thinking about buying a new Alltec Projector Screen and wondering what size to get?

Well use our custom Viewing Distance Calculator. For additional help in selecting the right Alltec projector screen, please feel free to give us a toll-free call at 800.352.6140.


The calculator needs three pieces of information:

  1. How far you sit from the screen, measured in feet.
  2. What shape/aspect Ratio is your screen?
  3. What is the size of the screen? You may enter either the diagonal screen size or the screen width. (If you enter screen width, don’t forget to check the appropriate ratio button)
If you do not specify a viewing distance, the calculator will tell you what the optimal seating distance is for the selected screen size.

The calculator calculates the following:

Viewing angle: Based on the inputs, this is the viewing angle or arc for your set up.

Maximum recommended viewing distance: Suggests a viewing distance of three to six screen widths for video. This corresponds to the point at which most people will begin having trouble picking out details and reading the screen. Probably too far away to be effective for home theater, OK for everyday TV viewing. Most people are comfortable watching TV between this distance and half this distance.

Maximum SMPTE recommended viewing distance: SMPTE standard EG-18-1994 recommends a minimum viewing angle of 30 degrees for movie theaters. This seems to be becoming a de facto standard for front projection home theaters also. Viewing from this distance or closer will result in a more immersive experience, and also lessen eye strain caused by watching a smaller image in a dark room.

Maximum and Recommended THX viewing distances: THX also publishes standards for movie theaters to adhere to for THX certification. THX requires that the back row of seats in a theater have at least a 26 degree viewing angle and recommends a 36 degree viewing angle.

SMPTE and THX screen widths: Based on the viewing distance supplied to the calculator, these are the minimum screen widths required to meet the SMPTE and THX recommendations discussed above.

Viewing Distances based on Visual Perception: These distances are calculated based on the resolving power of the human eye, or visual perception. The human eye with 20/20 vision can detect or resolve details as small as 1/60th of a degree of arc. These distances represent the point beyond which some of the detail in the picture is no longer able to be resolved and “blends” with adjacent detail.


(This calculator is intended only to give a general idea of proper viewing distances and angles. You need to experiment and find out what works for you and your situation. Your actual mileage may vary.)

  Viewing Distance Calculator

1. Distance to main viewing location: feet
2. Choose Screen Shape: 4:3 (Standard TV Shape)   16:9 (Widescreen TV Shape)
3. Choose Screen Size: (Enter either a diagonal screen size or width):
Choose  Diagonal Size =  inches 
or Width = inches


deg. Current Viewing angle

Feet Maximum recommended viewing distance

Feet Maximum recommended SMPTE viewing distance (30 degree viewing angle)

Feet Maximum THX viewing distance (26 degree viewing angle)

Feet Recommended THX viewing distance (36 degree viewing angle)

Screen size to achieve SMPTE minimum viewing angle

” wide = ” 4:3 diagonal or ” 16:9 diagonal

Screen size to achieve THX recommended viewing angle

” wide = ” 4:3 diagonal or ” 16:9 diagonal

Viewing Distances Based on Visual Perception

Feet Maximum Viewing Distance for NTSC/PAL(720×480/720×576)

Feet Maximum Viewing Distance for HDTV(Fully resolved 1080i; 1920 x 1080)




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