Projector Screen Size Calculator

Every projector has a throw ratio printed in its specs. The throw ratio is the relationship between throw distance (lens to screen) and image width:

throw_ratio = throw_distance / image_width

If a projector has a throw ratio of 1.5 and you place it 10 ft from the wall, the image width is 10 / 1.5 = 6.67 ft.

From width, you get the diagonal using the aspect ratio:

image_height = image_width / aspect diagonal = sqrt(width^2 + height^2)

Common aspect ratios:

• 16:9 (1.778) — modern HDTV, most projectors and content
• 16:10 (1.6) — older laptops, business projectors
• 4:3 (1.333) — old TVs, presentations
• 2.35:1 — cinema scope, anamorphic widescreen

Throw ratio categories:

• Long throw (1.8+): old conference room projectors, distant placement
• Standard throw (1.0 to 1.8): most home theater projectors
• Short throw (0.4 to 1.0): mounted close to the wall
• Ultra-short throw (under 0.4): cabinet placement directly below screen

For a 100-inch diagonal 16:9 image (87.2 inch wide), you need a throw distance of roughly:

• Long throw 2.0: 174 inches (14.5 ft)
• Standard 1.5: 131 inches (10.9 ft)
• Short throw 0.7: 61 inches (5.1 ft)
• Ultra-short 0.3: 26 inches (2.2 ft)

Practical considerations:

• Zoom lens projectors give you a range, not one fixed throw ratio. A 1.2x zoom at 1.5 base ratio means 1.5 to 1.8 throw range.
• Vertical and horizontal lens shift add placement flexibility — you can move the projector off-center without keystoning.
• A bright room needs more lumens per square foot. As image size doubles, light hitting the screen drops to one quarter (inverse square law for brightness per area). A 200-inch screen requires roughly 4x the lumens of a 100-inch screen for the same perceived brightness.
• Most home users overshoot screen size. A 100-inch screen at 12 feet viewing distance is about right; 150 inches at the same distance is exhausting to watch.