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About this tool
Find the right TV size, seating distance and wall-mount height using SMPTE and THX viewing angles plus pixel acuity limits.
This TV viewing distance calculator works out the horizontal viewing angle your screen fills from where you actually sit, and compares it with the SMPTE minimum of 30° and the THX recommendation of 36°. It also applies the pixel acuity limit — the distance at which one pixel subtends one arcminute, the finest detail 20/20 vision can resolve — so you can see whether 4K or 8K is doing anything from your sofa. Finally it gives the wall-mount height that puts the centre of the screen level with your seated eyes.
Open TV Viewing Distance Calculator on AltFTool — it loads instantly in your browser.
Enter "Screen diagonal (inches)" or tap one of the 32", 43", 55", 65", 75" and 85" presets, then "Seating distance from screen (cm)", a Resolution from HD Ready (720p) to 8K UHD (4320p), the Aspect ratio, and "Seated eye height from floor (cm)".
Compare "Viewing angle from your seat" with the SMPTE 30° seating distance, THX 36° seating distance and "Closest sensible seat (THX 40°)" rows, and with "Ideal screen size from" your distance, to decide whether to move the sofa or change screen size.
The "Sit within this to resolve every pixel" row gives the acuity limit for your resolution, and the "Wall-mount height" card gives Screen centre above floor, Bottom edge, Top edge and the upward look to the top edge; "Copy result" copies the set.
SMPTE's 30° and THX's 36°/40° angles are applied directly to your numbers.
Shows the exact distance beyond which extra pixels stop being resolvable.
Gives the centre, top and bottom heights plus the upward neck angle.
About 2.3 m (7.5 ft) gives the SMPTE 30° angle, and roughly 1.9 m (6.1 ft) hits the THX 36° recommendation. Sitting closer than about 1.7 m puts the screen past 40°, at which point you have to move your eyes across the picture.
At 3 m a 16:9 screen of about 73 inches gives the SMPTE 30° angle and about 98 inches reaches the THX 40° maximum. In practice most people pick something in the 65–85 inch band for that distance, allowing for wall space and budget.
Only if you sit inside the pixel acuity limit. For a 55-inch 4K panel that limit is about 1.1 m; for a 65-inch it is roughly 1.3 m. Most living rooms are further back than that, which is why a bigger screen usually improves picture more than more pixels.
Put the centre of the screen level with your eyes when seated, typically about 105 cm from the floor on a normal sofa. For a 55-inch 16:9 panel that puts the bottom edge near 71 cm. Keep the top of the screen within roughly 15° above your line of sight to avoid neck strain.
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