Things You'll Need:
- Small objects
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Step 1
Examine your ruler. You will see two sets of lines. The first set of lines are longer, farther apart and numbered. These are called centimeters, or cm for short. The second set of lines are thinner and closer together. They fall in between the larger numbers. These are called millimeters or mm for short. They are not numbered. There are 10 millimeters in each centimeter.
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Step 2
Pick a small object to measure. This can be a pencil, paper clip, penny or refrigerator magnet. Whatever you have on hand will do.
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Step 3
Place the end of your object, such as the eraser on a pencil, against the beginning edge of the ruler. Make sure they line up perfectly.
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Step 4
Place your finger on the mark where the object ends, then remove the object.
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Step 5
Look for the last centimeter mark that your object passed. It is possible that the object landed directly on a numbered centimeter mark. For example, if your pencil ends on the 5 centimeter mark, then it is 5 centimeters long. If, however, it went slightly past the 5 centimeter mark, write down 5 centimeters and continue to the next step.
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Step 6
Count the little lines after the last centimeter mark your object passed until you land on the line that matches the end of the object. So if your pencil ends three lines after the 5 centimeter mark, it would be 5 centimeters and 3 millimeters long.
