What is an aspect ratio?

Answer 1

An aspect ratio is the width by height dimensions (the ratio) of a display screen. It's often used in terms of a movie screen, TV, or computer monitor. The standard aspect ratio for television is 4:3 (aka Academy Standard or 1.33:1). In other words, if the width of the screen is four inches, the height would be three inches. If the width is eight inches, the height would be six inches. If the width is 16 inches, the height would be 12. Wide-screen television broadcasts and DVDs are 16:9 (aka 1.78:1). Modern movies are either 1.85:1 (aka Widescreen, Academy Flat or Academy for short) or 2.35:1 (aka Panavision, Cinemascope or just Scope). Technically, Panavision is 2.39:1, but is still commonly referred to as 2.35:1. There are also quite a few aspects that have been used by the movie industry, but are no longer used.

Answer 2

The aspect ratio for screens is basically it's dimensions (length and width)

For example, an aspect ratio of 4:3 means it is 4 units long by three units wide.

The aspect ratio of Standard Defenition TVs and movies are usually 4:3, while high definition is normally 16:9, or sometimes 2.35:1.

If you watch an HD movie on a standard TV, then it will fill in the remaining area by letterboxing it.

If you have a 16:9 tv, and watch an older, 4:3 movie, then it fills in the remaining area by pillarboxing it.

Aspect ratios can vary between different videos and screens. Common aspect ratios are:

4:3

16:9

2.35:1

2.36:1

15:9

2:1

2.39:1

20:9