Why diagonal alone does not tell the full story
Screen diagonal is the most commonly advertised measurement, but two screens with the same diagonal can have very different usable areas depending on their aspect ratio. A 27-inch ultrawide (21:9) is significantly wider and less tall than a 27-inch standard monitor (16:9), even though both measure 27 inches corner to corner.
Understanding actual width and height is useful when planning a desk setup, comparing workspace for side-by-side windows, estimating viewing distance, or simply verifying whether a screen will fit a specific space.
Width = Diagonal × ratio_w / √(ratio_w² + ratio_h²)
The aspect ratio components define the proportions; the Pythagorean theorem relates the diagonal to those proportions.
Height = Diagonal × ratio_h / √(ratio_w² + ratio_h²)
Same relationship applied to the height dimension.
Area = Width × Height
Total screen area in square inches or square centimetres.