Calculating a 16:9 Ratio

Sometimes, clients want their 16 x 9 video at the correct aspect ratio but they want it smaller (or bigger...gah) and it's not always easy to know what an odd size for 16:9 is. Here's what I do.

16:9 is a ratio that's .5625

9 divided by 16 = .5625
9 divided by .5625 = 16
16 times .5625 = 9

You can think of it like this:

Small divided by Big = .5625
Small divided by .5625 = Big
Big times .5625 = Small

Or even:

Height divided by Width = .5625
Height times .5625 = Width
Width times .5625 = Height

So, knowing that, if they want a video that's say some weirdo size of 900 wide you can go 900 times .5625 and know that the height should be 506, so you set your encoder/transcoder to make it 900 x 506 (try and keep them multiples of two, btw. No one will notice if it's a pixel or two off.)

(In case you're curious 4:3 (ie..640 x 480) works the same way only the magic number is .75)