TV Size Calculator
Estimate screen dimensions from seating distance and a selected viewing angle reference.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
The calculator converts a horizontal viewing-angle reference into screen dimensions. THX describes a 36° angle from the farthest cinema seat; SMPTE ST 2080-3 specifies a 30° maximum horizontal angle for a reference display. These are different viewing contexts, not universal home-TV recommendations. The distance output is a simple 2.5× diagonal reference.
Worked example
calculated with the default values below
Seating distance 9 ft · Viewing experience THX (36°) · Aspect ratio 16:9 widescreen Estimated diagonal (viewing-angle reference) 80.5 in · Screen width 70.2 in · Screen height 39.5 in · Distance at 2.5× diagonal (reference) 16.8 ft
Data sources
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
W = 24D×tan(α÷2); H = W÷r; d = √(W²+H²); C = 2.5d÷12
- D
- Viewing distance (ft)
- α
- Viewing angle (°)
- r
- Aspect ratio (width/height)
- W
- Screen width (in)
- H
- Screen height (in)
- d
- Screen diagonal (in)
W=24D·tan(α/2); H=W/r; d=√(W²+H²); reference distance C=2.5d/12 ft. THX preset 36°; SMPTE ST 2080-3 horizontal reference 30°; other presets are user-selected examples. C is a heuristic, not a comfort standard.
Frequently asked questions
Why does the THX setting recommend a larger screen than basic?
The THX preset uses 36°, matching THX guidance for the farthest cinema seat. SMPTE ST 2080-3 gives a 30° horizontal reference limit for a reference display. These serve different contexts. The 2.5× diagonal distance is a simple reference heuristic, not a universal comfort limit.