Calculating the stitch count is fairly easy. Even for linen.
You would take the number of stitches for the project...(i.e. 100 x 75)
Now you divide the project count by the number of stitches you wish to stitch the project in. For instance:
My project is 100 stitches wide by 75 high
I decide that I want to stitch this on 28 count linen. Knowing that you stitch over 2 on 28 count linen, you would divide your project by 14. Thus, 100 wide in 28 linen would be 7.15 and 75 high would be 5.36. That is how much linen you would need. Remembering of course to add 2-3 inches on each side for finishing.
On 32 count linen, divide by 16, the same piece would come out to 6.25 by 4.69.
On 36 count linen, divide by 18, the same piece would come out to 5.56 by 4.17
etc etc
This is how you would calculate the size of fabric needed for any project no matter what fabric you use....Aida, evenweave or linen.
I hope this is clear.