Reading a Ruler: Units of Measurement on a Ruler

Get Tips for Reading Ruler Measurements

Kid with ruler
You will have learned how to use a ruler back in your school days when you would have used one to draw margins or all kinds of lines. You would also have learned about different scales for measuring length or distance, etc. You've probably even learned how to do fun crafts using a ruler. A ruler or a tape measure is a useful device to measure lengths. Knowing how to use and read the units of measure is a basic skill that has uses in various applications including building, manufacturing, creating objects such as furniture, and measuring for interiors. Listed below are some easy guidelines on how to read and use a ruler.

Step 1

Scales of measurement. Every ruler has two sides, each depicting a scale of measurement. You need to know how to read both sides. On one side, you will find the metric system for marking length and on the other side is the English scale. The metric scale measures length or distance in millimeters and centimeters, whereas the English scale uses inches and feet.

Step 2

Using the metric scale. Let's talk about metric measurements first. A standard ruler measurement is usually about a foot long, or in metric terms, about 30 centimeters. You will find the ruler marked with lines that are designated with numbers from 1 to 30 and between each set of numbers, there are smaller lines that indicate the number of millimeters. Ten millimeters (or mm) equal 1 centimeter (or cm), 100 cm equals 1 meter, and so on. To measure the length between two points on a paper or other medium, place the ruler with the first centimeter line (which can be tagged as zero) on the first point. Mark the number at which the second dot on the paper corresponds to the centimeter reading. For example, with one point placed against the zero mark and the second point shows a reading of 3. In this case, the distance in centimeters between the two points is 3 cm. If the point is actually placed at a point beyond 3 but well within the line depicting 4, count the smaller lines that show the millimeter scale and count the number of lines at which the point rests - say at the 5th small line, in which case the distance between the two points is 3.5 cm or 35 mm.

Step 3

Using the English scale. The other side of the ruler measures length in feet and inches. This is the scale of ruler measurement used in the United States. One foot equals 12 inches, and between each inch are smaller markings in sets of eight. These are referred to as eighths of an inch. Following the same instructions as in step two, you can find out the distance in inches and eighths of inches. Using the same two points in the example above, the length will read as 1 2/8 in.

Step 4

Important tips. While using and reading a ruler make sure that you place and hold it firmly against paper or other medium. Keep it in a straight line always, whether placing it horizontally or vertically. To validate your measurements, you can always take down readings in both centimeters and inches and divide the metric measurement by 2.54. If the reading you've taken is accurate, the quotient of this division will equal the number of inches you've measured.

You now know how easy it is to read measurements on a ruler. You can replicate the same system when measuring larger lengths, but in those instances, the measurements will move into meters and feet.


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