Yeah, that's impossible. Your typical ruler has inches that are divided into eight sections.

This means that the first hash mark after the 1-inch line will be 1.125 inches, then 1.25 inches, 1.375 inches, 1.5 inches, then 1.625 inches. That last one will be the 5th mark after the one-inch line, and the measurement you want is about a millimeter before it. Unless you have a ruler that divides into hundredths of an inch, you will have to take your best guess.

This means that the first hash mark after the 1-inch line will be 1.125 inches, then 1.25 inches, 1.375 inches, 1.5 inches, then 1.625 inches. That last one will be the 5th mark after the one-inch line, and the measurement you want is about a millimeter before it. Unless you have a ruler that divides into hundredths of an inch, you will have to take your best guess.