Projector Screen Size Calculator with THX & SMPTE Recommendations

Free calculator that converts your projector screen diagonal into width, height, area and pixel density across every common aspect ratio (16:9, 4:3, 16:10, 21:9, 2.35:1, 1.85:1). Includes professional viewing-distance recommendations from THX (36° viewing angle, cinematic) and SMPTE (30°, broadcast standard), plus a 4K-resolvable minimum so you do not sit so close that pixels become visible.

How to size your projector screen

1
Pick your aspect ratio

16:9 for streaming and most home use, 2.35:1 for CinemaScope movies, 4:3 for legacy presentations.

2
Enter the diagonal

In inches if you are buying a fixed screen, in centimetres if you are wall-projecting and only know your wall width.

3
Read the dimensions

Width and height tell you how much wall space you need — leave 20–30 cm of dark border around the image for best contrast.

4
Plan seating distance

Use THX for serious home cinema, SMPTE for general use. If you fall outside both, the screen is either too big or too small for the room.

Get screen dimensions and the right seating distance — based on THX and SMPTE standards

Recommended viewing distance

Reverse: my room → max screen

Know the distance from your seat to the wall? Get the largest screen diagonal that still fits THX/SMPTE viewing recommendations.

Room mockup

Features

All dimensions at once THX & SMPTE recommendations 4K minimum distance Visual room mockup 6 aspect ratios

FAQ

What is the difference between THX and SMPTE viewing distance?

THX recommends a viewing angle of 36°, which is more immersive and cinematic. SMPTE recommends 30°, which is the broadcast industry standard and more comfortable for general viewing. THX puts you closer to the screen relative to its width; SMPTE is a touch farther.

How big a screen should I get for my room?

Start by measuring how far the primary seat is from where the screen would go. Divide that distance (in metres) by 1.866 for SMPTE (30°) — the result is the recommended image width. For a 16:9 screen, multiply width by 1.147 to get the diagonal in metres, then × 39.37 for inches.

Can I sit too close to a 4K projector?

Yes — even at 4K, individual pixels become visible if you sit closer than the screen width. The "Minimum (4K-resolvable)" recommendation is the closest you can sit at 4K before that happens. At 1080p the minimum is roughly twice the screen width.

Why does CinemaScope (2.35:1) look smaller than 16:9 at the same diagonal?

A 100" 2.35:1 screen has the same diagonal but is wider and shorter than a 100" 16:9 screen. People often switch to a constant-image-height (CIH) setup where 2.35:1 is wider than 16:9 — that requires either a wider screen or anamorphic lens.

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Who is this tool for?
📽️ Projector Owners
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