Screen size calculator
This screen size calculator takes the diagonal, aspect ratio and resolution and gives you width and height in centimetres and inches, the pixel density and the retina distance.
Example: Screen diagonal 27 ″ · Aspect ratio: 16:9 · Resolution: 2560 × 1440 (QHD) → Result: 59.8 × 33.6 cm at 109 ppi. Source: Wikipedia – Pixeldichte (ppi): pixel diagonal divided by image diagonal in inches. Updated: .
How it is calculated
From diagonal d and aspect ratio W:H, width = d·W/√(W²+H²) and height = d·H/√(W²+H²). A 27-inch 16:9 monitor is 59.8 cm wide and 33.6 cm tall (23.5 × 13.2 in).
How it is calculated
The diagonal is split in the ratio of the sides (Pythagoras), 1 inch is 2.54 cm. Pixel density is the pixel diagonal √(width² + height²) divided by the diagonal in inches. The retina distance is the distance from which one pixel subtends one arcminute: distance = pixel pitch / (2·tan(1′/2)), about 3438 / ppi inches.
Good to know
- 27 inches at 2560 × 1440 gives about 109 ppi, at 3840 × 2160 about 163 ppi – same size, much sharper.
- An ultrawide (21:9) with the same diagonal is wider but less tall than a 16:9 monitor.
- The stated diagonal is the image area without bezel; the case and stand are larger.
Frequently asked questions
How do I convert inches to cm for a screen?
With 1 inch = 2.54 cm: 27 inches is a 68.6 cm diagonal. For width and height you also need the aspect ratio; at 16:9 it is 59.8 × 33.6 cm.
How do you calculate pixel density (ppi)?
The square root of width² plus height² (in pixels) divided by the diagonal in inches. For 2560 × 1440 at 27 inches that is about 109 ppi.
How far should I sit from the screen?
The retina distance tells you when pixels stop standing out individually: about 80 cm (31 in) at 109 ppi. Closer, pixels show; further away, nothing gets sharper.
How big is a 24-inch 16:9 monitor?
About 53.1 cm wide and 29.9 cm tall, with a screen area of roughly 1588 cm².
Sources and legal basis
- Wikipedia – Pixeldichte (ppi): pixel diagonal divided by image diagonal in inches
- Wikipedia – Zoll (Einheit): 1 Zoll = 25,4 mm (exakt)
- Wikipedia – Sehschärfe (visual acuity): resolution limit of the eye of about one arcminute
As of: · Editorial policy
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