Rulers are quite easy to read. They deal with centimeters, millimeters inches. On the centimeter side the smallest lines show the millimeters and the largest ones show centimeters. Milimeters are 1/10th of a centimeter and if you measure 5 marks aftera centimeter, it is 1.5 centimeter. On the rulers marked in 8ths, every point is 1/8th of an inch. Similarly on a ruler marked in 16ths every point is 1/16th of an inch.