75.75 x 13.57 will get you close. BUT that will shift based on your
printer and monitor settings. So start there, and then print and adjust
based on the output.

wrote:
I want to make my grid into perfect squares: row height = column
width.

The problem is, they seem to use different measurement schemes. Is
there some conversion factor, or way to set columns to use the same
measurement scheme as rows?

I need them to print out as perfect squares.