How to Read a Ruler
Sometimes, the art of measuring things seems a complete mystery. That is, unless you are familiar with reading a ruler accurately. Even if you are fairly sure you understand how to read one, check these steps to make sure you are obtaining an accurate measurement.
Required Materials
- 1 12-inch ruler
- 1 pencil
- 1 piece of paper
Instructions
- Rulers have two edges. One side of the ruler typically allows the user to obtain metric measurements, while the other side offers the ability to obtain English measurements, in inches.
- Let’s begin by looking at the metric side. The measurement unit on this side is centimeters (cm). The ruler is one foot, or 12 inches long. Twelve inches equals 30 centimeters. Therefore, the metric side is the one that contains numbers from 1 to 30.
- Notice that there are 9 lines between each centimeter. Each of these smaller lines represents 1 millimeter (mm). There are 10mm in one centimeter.
- Now, mark two points on the piece of paper with a pencil. For ease of use, be sure that the distance between the marks is smaller than the length of the ruler.
- Place one end of the ruler at the first mark. Hold that end steady and move the other end of the ruler until it connects to the second mark. Touch your finger or pencil to the point on the ruler that intersects the second mark.
- Look for the first number to the left of that point on the ruler. For example, if the mark is between 15 and 16, write down 15.
- Count the number of little marks between this number and the point you are touching on the ruler. This number indicates how many millimeters between the larger number and your mark. For example, if your point is on the fourth mark, there are 4mm between the first number and your mark.
- Putting it together: The distance between your marks is 15cm and 4mm. Because each millimeter is one-tenth of a centimeter, you may also write this in decimal form: 15.4cm.
- To measure these same marks in inches:
- Place the end of the side containing 12 numbers against the first mark, and hold this end still while moving the other end of the ruler until it connects with the second mark. Touch the ruler at this point.
- Locate the number to the left of your mark. This indicates the number of inches between your marks. Now, count the smaller lines between numbers. You will notice that there are seven lines, each representing one-eighth of an inch, between each number.
- The measurement between your two points in inches is the first number. If this number was 6, the distance between your points is 6 inches. More than likely, however, you also had several smaller lines between the 6 and your mark. These marks are described as eighths of an inch. If you counted three marks, for example, you would have a total of 6 and 3/8 inches between your marks.
Tips
- If you want to check your work, measure the distance in both inches and centimeters. Divide your result in inches by 2.54. This should equal your answer in inches.
- Hold the ruler steady when measuring. Moving the end of your ruler will result in an inaccurate measurement.