Why Do We Measure A TV Screen Diagonally?

I am a salesman at an electronics store. First off, from the best of my knowledge, no television is or has ever been a perfect square. That is, they are always wider left to right then they are up and down. Even your grandparents 300 pound tubes were set in an "aspect ratio" (left-right vs. Up-down ratio) of 4 to 3, which is expressed as 4:3. (for every 4 inches wide, it's 3 inches tall)Today we have no more televisions or monitors that are 4:3 because most t.v. Programs are being filmed in the ratio of 16:9. And if I'm not mistaken MOST movies have throughout modern history been filmed in this ratio. This is why the industry has moved towards "wide-screen" televisions with the 16:9 aspect ratio. My only disclaimer is that movie directors/producers can choose whatever aspect ratio they want so no matter what t.v. You have, the show or movie you are watching still may not fit "perfectly". Which is why you may still see black bars on the top and bottom of your t.v. (or the bars would be on the left and right if you are watching a movie or show which is filmed in 4:3)Interestingly enough, since movies have almost always been in this format, and all televisions are now 16:9, the term "wide-screen" is very soon going to be obsolete. Since t.v.'s only come in two standard aspect ratios, you can't really fake how big it is. For instance, you can't find a t.v. With an aspect ratio of 50:2 and advertise it as a 100" television. This t.v. Would only be 4 inches tall! (talk about a lost leader)As for WHY we measure diagonally, I can only guess that it is simplification. Once you know what aspect ratio you're dealing with, you only need one number to represent how big the t.v. Is. You can simply call it a "36 inch television", rather than a "32 inch left to right and 18 inch bottom to top television".

Mathematically, the diagonal of the rectangle shape TV shows the total width of the TV.

The system for measuring a TV diagonally became a common method in most electronic stores in the early 80's. Before this standard of measurement different stores used different measurements (some measured Diagonally and Some Horizontal)

"Old sets were measured diagonally, new sets
horizontally. But consumer confusion has led to Most stores deciding to measure
new TVs diagonally too. Your best bet? Take a tape measure and check
for yourself. And remember -- the size they list is only the size of
the screen, not the TV cabinet." "Quoted From an 1980's article (actual date wasn't available)"

Television screens are measured diagonally because the first picture tubes were round. Early sets showed the entire round surface, but later sets masked off to a rectangle. Rectangular tubes are more difficult to manufacture and weren't in common use until around the late 60's. So the early tubes were measured by their diameter. After masking this is the diagonal.

I would venture to say that it is simply marketing. A 36 inch diagonal television sounds larger than a 32 inch horizontal television despite their identical size.

No one really knows why it's just how it's been done for ever