Home Cinema & AV
TV Size vs Viewing Distance Calculator
Recommended screen size for a seat distance
Updated July 12, 2026 · Live
What this tool does
Recommends a screen diagonal from your viewing distance and a preferred viewing angle, using the SMPTE and THX standards.
Enter the viewing distance and your preferred viewing angle; the calculator returns the recommended screen diagonal.
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Formula Used
Recommends a screen diagonal from your viewing distance and a preferred viewing angle, using the SMPTE and THX standards. It runs entirely in your browser and shows the working, so you can check every step against your own figures.
How the tv size vs viewing distance calculator works
The screen width that fills a chosen horizontal viewing angle at your seat is twice the distance times the tangent of half the angle. For a 16:9 screen the diagonal follows from the width, and the tool quotes it in inches. A wider angle fills more of your field of view and feels more cinematic.
What you enter
Enter the viewing distance and your preferred viewing angle; the calculator returns the recommended screen diagonal. Every field is editable, and the result recalculates the moment you change a value.
Reading the result
SMPTE’s 30° is the reference for mixed film and TV; THX’s 36–40° is more immersive for movies. Pick the angle for the experience you want, then round to the nearest screen size sold.
Safe by design
This is pure geometry and acoustics — there is no safety threshold anyone acts on. It plans what you can see and hear, not any electrical or structural work.
Assumptions and limits
This sizes for a horizontal viewing angle and assumes 16:9. Resolution matters too — sitting close to a low-resolution screen makes pixels visible — and personal preference varies. Treat it as a well-grounded starting size.
Using it with the rest of BuildMetricLab
This calculator is one step in planning the job. Pair it with the related tools in this category and across BuildMetricLab to go from a single figure to a full costed plan — a sizing figure feeds a cost estimate, a cost estimate feeds a project budget, and each result carries straight into the next tool. Every BuildMetricLab tool runs entirely in your browser — no sign-up, nothing sent to a server, and the formula is shown on the page so the maths can be audited.
Sources & methodology
Recommends a screen diagonal from your viewing distance and a preferred viewing angle, using the SMPTE and THX standards. Every result is calculated from the values you enter, all inputs are editable, and no time-sensitive prices or rates are embedded.
Frequently asked questions
What viewing angle should I pick?
SMPTE recommends about 30° for general viewing; THX suggests 36-40° for a more immersive cinema feel. Wider means a bigger screen for the same seat.
Can a TV be too big?
It can be, depending on the source resolution and how close you sit — very wide viewing angles at low resolution can make pixel structure visible or require more eye movement across the image. This calculator only computes geometry from distance and angle; it does not account for source resolution.
Does this work for projectors too?
Yes, the geometry is identical. For projectors, also check the throw ratio with the projector-throw tool.
Is the diagonal in inches, and what aspect ratio is assumed?
Yes — screen sizes in the US are quoted as diagonal inches, so the result from this calculator is given in inches. The calculation assumes a 16:9 aspect ratio, which covers most TVs and many projector screens; a different aspect ratio will give a slightly different diagonal for the same width.
Spotted something off?
Calculations or display — let us know.