Screen Size
Calculator

Using the aspect ratio (width:height) and the diagonal measurement, the calculator applies the Pythagorean theorem: diagonal² = width² + height², combined with the aspect ratio to solve for both width and height individually. A 16:9 screen's width and height are in that same 16:9 proportion while satisfying the diagonal constraint.

Diagonal size became the industry convention going back to CRT tube manufacturing, where the diagonal was the most consistent measurable dimension across different tube shapes, and it has simply persisted as the standard marketing figure even though width and height (which depend on aspect ratio) are often more practically relevant for space planning.

Diagonal size alone doesn't determine shape, aspect ratio does, so a 27-inch 16:9 monitor is noticeably wider and shorter than a 27-inch 4:3 monitor of the same diagonal, since the same diagonal length is being distributed differently between width and height. This is why aspect ratio must be known alongside diagonal size to get true dimensions.

Knowing the actual width and height (not just the diagonal) tells you whether a screen will physically fit a desk, wall, or entertainment unit, and helps compare viewing area fairly between screens of different aspect ratios advertised at the same diagonal size. It turns a marketing number into a concrete physical footprint.

Yes, once you know a screen's actual width or height in inches, dividing the horizontal pixel resolution by that width gives pixels per inch (PPI), which determines how sharp and fine text and images will appear at normal viewing distance. Larger diagonal screens with the same resolution have lower PPI and appear less sharp up close.