Screen Size Calculator
Convert a screen diagonal into width, height and area for any aspect ratio.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Screen diagonal alone does not determine width and height; aspect ratio matters. Dimensions and PPI are calculated from the entered diagonal, aspect ratio and horizontal pixel count. The viewing-distance value is a simple 1.6× diagonal planning reference, not a standard or individualized comfort recommendation.
Worked example
calculated with the default values below
Screen diagonal 55 in · Aspect ratio 16:9 widescreen · Native resolution width 3,840 px Width 47.94 in · Height 26.96 in · Width 121.8 cm · Height 68.5 cm · Screen area 1,292.6 sq in · Pixel density 80.1 ppi · Simple viewing-distance reference 7.3 ft
General background references
Disclaimer
These calculators give general estimates. Sizing, pricing, availability and standards vary by brand, retailer and country, so treat the output as a starting point and confirm it against the seller's or authority's own figures.
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
h = D ÷ √(1 + a²); w = ah; PPI = R ÷ w; d = 1.6D ÷ 12
- D
- Diagonal (in)
- a
- Aspect ratio (e.g. 16 ÷ 9)
- w/h
- Screen width/height (in)
- R
- Horizontal pixels
- PPI
- Pixels per inch
Dimensions are inferred from diagonal and aspect ratio; PPI uses entered horizontal pixels divided by screen width. Viewing-distance output is a fixed 1.6× diagonal reference, not an individualized recommendation.
Frequently asked questions
Why does a 21:9 screen show less area than a 16:9 at 55 inches?
Diagonal measures the corner-to-corner length, not area, so a wider 21:9 panel packs a shorter height into the same 55 inch diagonal than a 16:9 one. The tool derives width and height from the aspect ratio, then multiplies them for area and divides the resolution width by width for pixel density, about 80 ppi at 3840 across a 48 inch width. Viewing distance scales from the diagonal at 1.6 times.