Metric rulers are easy to read. They deal with centimeters (abbreviated cm) and millimeters (abbreviated mm) only. Because the metric system is based on the decimal system just like our monetary system is, you won’t have to worry about fractions. Measurements in the metric system are written using decimals.
Take a look at the following Metric Ruler.
The larger lines with numbers are centimeters (cm), and the smallest lines are millimeters (mm). Since there are 10 mm in 1 cm, millimeters are 0.1 (1/10th) of a centimeter. If you measure an object that is 7 marks longer than 1 cm, it is 1.7 cm or 17 mm long. If the object’s length falls half-way between the 1.7 cm and 1.8 cm marks, it is 1.75 cm or 17.5 mm in length. If the measurement is not exactly half-way between two mm marks, you can estimate the measurement. For example if it is closer to 17 mm than to 18 mm, you might determine that it is 17.2 mm or 17.3 mm.