Custom Thumbnail Dimensions for YouTube


I Love YTtalk
I have always heard that there's a couple of custom thumbnail sizes that are best but I am meant to be doing a video about them soon so I want to make sure that I not only include the sizes I usually use but what others use too so I get it completely right, so what do you use yourself?

Personally I have been using a mix of 1280px x 720px and 640px x 360px, they seem to work well for me and I havent had any issues with them so it feels right to me using those sizes.

What produces the best results in fitting and quality for you all?

Thanks, hopefully this will help me with this video and also others here wonder the same thing as I know its been cropping up a lot with most of us having custom thumbnails now.
"Please upload as large an image as possible (suggested: 1280x720), since the image will also be used as the preview image when your video is embedded on other sites. You can upload a JPG, GIF, BMP, or PNG file. Maximum file size is 2MB."

I always use 1280 x 720 now and fits perfectly with about a 10 x 10 boarder top and bottom. The boarder needs to be a bit bigger if you plan to embed, I don't ever embed except on yttalk so I don't bother :p
Thanks, this was just the info i was looking for. My channel JUST got enabled for custom thumbnails. I'm super excited haha