video - What is the right way to calculate 1080p 720p 360p 240p quality?

I'm working on a video hosting project and I would like to know if I'm converting my videos quality the right way.

my equation is: newY=(y/x)*newX

so 1080p is:

    1080x460
   than 720p
    720x306
   ...
    480x204
    360x154
    240x102
    144x60

My problem is 360 and below comes out in a terrible quality. comparing that to youtube I'm wondering if they are actually changing the video resolution or just changing the kb/s?

Answer

1080 describes the vertical resolution of a video. In your question you're using it as the horizontal resolution. As techie mentioned in the comments, common video resolutions include:

• 1920 x 1080


• 1280 x 720


• 720 x 480


• 480 x 360


• 640 x 360