grid failures

Lately, I've been trying to use more grids with my work this is the latest failure and somewhat successes. I want to use grids to enlarge drawings in my sketchbook!

lately, I've had trouble with scaling. The paper is just too small. like an inch off every time.

The other problem was not using a graphite pencil instead I used a piece of charcoal.

It cant be erased on this paper which is surprising on smaller versions of the paper it comes right out.