Have you ever tried to post a YouTube video only to find it was too large or too small for your WordPress site? If you turn on Text view and start trying to do this yourself you can end up with a hot mess that’s out of proportion. This is called “Aspect Ratio” — if you increase (or decrease) on side of the video, the change you make to the other side must also change to be in proportion. Don’t worry you don’t have to be a math whiz to figure this out… let YouTube do the calculating!
Right below the blue code (the code you’ll copy and paste onto your page or post) are a size menu and when clicked you’ll get an option for custom sizes. When you click on Custom Sizes in an instant you’ll see boxes to calculate width and height. The first box is for the width, so put in how wide you’d like the video to be. The default width is 420 so go wider or narrower depending on whether you want the video to be larger or smaller.
YouTube is brilliant! It will fill in the height for you and it will be in proportion to the width you entered.
YouTube is double-brilliant! After it does the math for you, it will put these new measurements in the code box so all you have to do is copy and paste.
Thank, goodnes… no math!