This is the paper I use to make fan comics. It is A4 size, which is slightly longer than the US Letter size.
However, there is a limit as where you can draw because if you might draw over the tachikiri. The word literally means “to cut off” and decribes what might literally happen to your picture if drawn in the wrong place. The below image shows where the best place to draw is. The blue box represents the edges of the page; the green box the best area to put important works on.
Here is a closeup of the area that shows where the tachikiri is-the line the arrows are pointing.
I hope this is enlightening in anyway.