And the size for bookmark icon is mostly 16×16 pixel square.
Below are step on how to add favicon to your blogger blog.
You have to get your favicon image ready or you click here to create one for yourself
Now after you have finish creating it all you need to do is to upload it to your file Manager and make it is safe.
Now go to your blogger dashboard and then select the blog you choose to work on.
On Blogger dashboard page scroll down and click on layout.
On the layout page at the top left side before the the navbar gadget you will find the favicon just click on the edit button.
Now upload your favicon and then click on the save button and then go to your blog and refresh it that’s all.
I hope this will help you. Don’t forget to drop your comment below thanks.