TV Screen Size Converter

A diagonal is not a width

Screen sizes are sold by the diagonal because it is one number that works for every aspect ratio — but it hides the shape. For a 16:9 screen, the width is the diagonal multiplied by 16 and divided by the square root of 337 (about 0.8716), and the height is the diagonal multiplied by 9 and divided by the same root (about 0.4903). A 55-inch TV is therefore about 121.8 cm wide and 68.5 cm tall, before any bezel or stand. That is why two televisions with the same diagonal can look completely different: a 21:9 ultrawide panel of the same diagonal is wider and shorter than a 16:9 one.

Common 16:9 screen sizes at a glance

Widths and heights below are for the screen itself, not the whole television — add a centimetre or two per side for the bezel, and check the manufacturer's full dimensions (including the stand) before buying furniture for it.

Will it fit the wall unit?

Measure the space, then compare the screen width plus bezel against it — not the diagonal. For wall mounting, also check the VESA bolt pattern on the back of the set, which is unrelated to the screen size, and confirm the mount's weight rating. A rough rule of thumb for viewing distance is one-and-a-half to two-and-a-half times the diagonal: for a 55-inch set that is roughly 2.1 to 3.5 metres, though personal preference and resolution matter more than any rule.

16:9, 21:9 and 4:3 — the aspect assumption matters

Almost every television sold today is 16:9, which is what this converter assumes by default. Computer monitors are often 21:9 ultrawide, and older CRT televisions were 4:3. Pick the right ratio above: at the same 55-inch diagonal, a 21:9 screen is about 128.9 cm wide but only 55.1 cm tall, while a 4:3 screen is 111.8 cm wide and 83.8 cm tall. Same diagonal, very different rectangle.