Hello,
It's a 7 mesh canvas so that means there are 7 holes per inch. If the total size of the sheet in inches is 13.5 x 21.5 just multiply those numbers by 7 and that will give you your total hole amounts for width and height. 13.5 x 7 = 94.5 and 21.5 x 7 = 150.5.
~Kriti @ EPC