TV Size / Viewing Distance Calculator
Sitting too close to a giant screen — or squinting at a tiny one? Enter how far you sit from the TV and get the recommended screen-size range from SMPTE and THX viewing-angle guidelines, plus the ideal mounting height for comfortable viewing.
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How to use this calculator
Measure from where your eyes sit to the TV screen in feet — couch to wall is the usual number. The calculator converts the SMPTE 30-degree minimum and THX 36-degree recommended viewing angles into screen diagonals, then picks the common TV sizes that fall inside the range.
Mount so the center of the screen sits at about 42 inches — average seated eye level.
How it works
For viewing distance D and viewing angle θ, screen diagonal = 2 × D × tan(θ/2). At 30° (SMPTE minimum) the factor is 0.536 × D; at 36° (THX recommended) it is 0.650 × D, with D in inches. Common sizes considered: 43, 50, 55, 65, 75, and 85 inches.
A 16:9 screen's height is about 49% of its diagonal, which sets the bottom-edge height when the center is mounted at 42 inches.
Frequently asked questions
What is the best viewing distance for a 4K TV?
With 4K resolution you can sit closer: THX recommends a 36-degree field of view, which for an 8-foot viewing distance lands around a 60-65 inch screen. For 1080p, sit a bit farther back or go smaller.
How high should I mount my TV?
Center the screen at seated eye level, about 42 inches from the floor. The calculator shows the matching bottom-edge height for your screen size.
Can a TV be too big for a room?
Only if you sit closer than the THX minimum — text gets hard to track and you will turn your head to follow action. Within the recommended range, most people wish they had gone bigger, not smaller.
How do you measure TV screen size?
Diagonally, corner to corner of the actual display (not the bezel). A 16:9 screen's height is about 49% of its diagonal.
Does room brightness matter for TV size?
Not for size, but for technology: bright rooms favor brighter LED/QLED panels, while dark home theaters get the most from OLED contrast.