Making a test "block" is the method that works for me.
1) Cut three strips "my" version of 2 inches - they are actually a smidge wider because of the space between the cutter blade and the ruler - approximately 6.5 inches long
2) Sew them together - using "my" version of a 1/4 inch seam
3) Press the seams - however you prefer - I usually press them all to one side - some people press them open
4) Measure across the result- this should be 5 inches by approximately 6.5 inches.
5) If the result is NOT 5 inches across the three strips, I need to do some adjusting -
a) If LESS than 5 inches - First, check the pressing to make sure there are no "pleats/crease" by the seams, - if that is okay, then I could place the ruler a bit differently so I get slightly wider strips - OR - I could make a slightly narrower seam
b) If MORE than 5 inches - cut the strips a smidge narrower - or - make the seams a smidge wider
Seams easier than messing around with those rulers.