To read a metric ruler, each individual line represents .10 (1/10) of a centimeter, or 1 millimeter. Notice when converting from centimeters to millimeters, the decimal point is moved one place to the right. To convert millimeters to centimeters, move the decimal point one place to the left. Look at the ruler below.
On a metric ruler, the numbers represent centimeters. The individual lines between the numbers represent millimeters. Each millimeter is one-tenth of a centimeter, so ten millimeters equals one centimeter. Before you start measuring, make sure that one end of the object is lined up with the 0 cm mark on the ruler.
Between each centimeter (cm) mark, there should be 10 smaller marks called millimeters (mm). Make sure you read the ruler from left to right. If you are measuring an object, align it with the left side of the zero mark on the ruler.
Instructions on how to use a metric ruler.. In the drawing below we show various options for cm and mm and how to correctly read the ruler; remember 10mm .
You can find out how to read a ruler from this article. Visit HowStuffWorks.com to learn more on how to read a ruler.