How screens are measured and what the inches actually tell you

Have you ever wondered why the screen on your 32-inch TV is way more than 10 times bigger than the display on your 3.2-inch phone? Or why the screen on your 3.7-inch smartphone is over twice as big as your old 2.4-inch dumbphone? The answer is most likely no, but here’s an explanation anyway. This is how screen sizes are measured and what the inches actually mean — why a 4-inch screen isn’t twice as big as a 2-inch screen.

Screens are nearly always measured diagonally, regardless of aspect ratio: from the lower corner of the screen to the upper corner of the screen. This length in inches is the screen size. Because the screen is measured diagonally and not in an area value derived from width x height, a 20-inch screen isn’t twice as big as a 10-inch screen: it’s 300% larger.

Let’s take a look at the example below. The picture shows a model of a 3.2-inch 16:9 screen.

This picture shows the same 3.2-inch screen cut into a 1.6-inch screen (half its inches).

So if you upgrade from a 3.7-inch screen to a 4.3-inch screen, for example, you’ll get more additional screen estate than you might think: 35% more, in round figures. Here’s a website that lets you compare screen sizes if you want to do further investigating.