How to Read a Metric Ruler in MM
The two main systems of measurement are the metric system, which is official in most parts of the world, and the U.S. standard system, which derives from the English measuring system. Although the United States still uses and teaches the standard system, metric rulers are common in the United States. In order to read a metric ruler, you must understand the relationship between millimeters (mm) and centimeters (cm).
Other People Are Reading
Instructions
-
-
1
Look at the edge of a paper clip or a dime. That's about the thickness of 1 millimeter. On a metric ruler, a millimeter appears as the distance between two very short lines. These short lines --- which some people call tick marks or hash marks --- run the full length of the ruler's edge.
-
2
Start at the first line on the left of the ruler (the zero point), and count each space to the right until you get to 10. You will notice that the line after the tenth space is much longer than the other lines, and has a 1 near it to indicate 1 centimeter. This means that 1 centimeter contains 10 millimeters. If we write this measurement down on paper, it looks like this: 1cm.
-
-
3
Lay the ruler down on the paper, and press your pencil against the edge of the ruler at the zero point. Draw a straight line that ends somewhere between the 1-centimeter line and the 2-centimeter line. We know that this line is longer than 1 centimeter, because we went past the 1-centimeter line, and we also know that it is shorter than 2 centimeters, because it doesn't quite reach the 2-centimeter line.
-
4
Write a 1 on your paper. This is the number of whole centimeters that our line contains. We know that our line also contains a fraction of another centimeter, so put a decimal point after the 1.
-
5
Starting at the 1-centimeter line, count the spaces between the millimeter lines to the right of the 1-centimeter line. Stop counting when you get to the end of the line you drew on the paper. Write this number after the decimal point. For example, if your line extended 4 millimeters past the 1-centimeter line, you would write "4" after the decimal point. That would give you a measurement of 1.4cm, which represents 1 centimeter plus 4 millimeters.
-
1
Tips & Warnings
Practice reading your metric ruler by measuring objects around you and writing down the measurements. Take several measurements, add them together, and try to figure out how many millimeters are in the result.
References
Resources
- Photo Credit ruler image by AGphotographer from Fotolia.com
