Students in the Unites States are raised learning that small units of measurements are inches, larger units are feet and miles and milk
and gasoline are measured by the gallon. They are weighed according to pounds and grow by inches. What they do not realize is that the rest of the world speaks a completely different language of measurement. Families in Europe, Asia, Africa and around the globe measure the distance to Grandma's house in kilometers, the weight of their babies in kilograms, and fill their gas tanks with liters of petrol.
When math teachers in the United States begin to consider how to teach metric conversions the first step is making students aware of the world they live in and the need for understanding the metric system. While metric measurements may seem simple because of their basis in the number 10, students in the United States will need to adjust their thinking to accept this foreign system.
A great starting point for teaching metric conversions is through visual examples. Teachers should prepare for this lesson by collecting items with both American standard measurements and metric equivalents. Below is a list of some sample items which serve as good visuals for introducing the prevalence of the metric system.
- measuring bowls, cups & spoons with both measurements shown
- a food scale or bathroom scale with both measurements shown
- a 2-liter bottle of soda and/or a juice bottle or milk jug
- common pantry items such as cereal or soup which have both measurements listed
- a map of a popular destination with a key shown only in kilometers
It should be explained that the metric system is all around us, even in the United States.
Units Worth Measuring
The most significant units worth addressing in a preliminary study of how to teach metric conversions are mass, length and capacity and their corresponding metric families — grams, meters and liters. From the examples above, the food items demonstrate mass, the map demonstrates length and the measuring bowls demonstrate capacity. From here, teachers must explain the difference between small measurements and larger measurements, ie. grams vs. kilograms, meters vs. kilometers, and liters vs. kiloliters
To help students become more familiar with these metric terms and prepare them for specific conversion problems, teachers and students can engage in a simple discussion focusing on which metric term would apply to certain situations. For instance, what is a bathtub filled with (a) meters or (b) liters, etc. Here are a few more examples.
- Does an elephant weigh grams or kilograms?
- Is the distance across town liters or kilometers?
- What measurement describes the weight of a computer — grams or liters?
- What measurement describes how much water is in a swimming pool ?
When considering how to teach metric conversion the best approach is to focus on the simplest and most common items for students. Students will have a sense that a pencil weighs less than a table, so using familiar classroom items generally helps make metric conversion problems easier.
Once students have a sense of the metric families (mass, length and capacity = grams, meters and liters) and a basic understanding of the larger and smaller measurements, metric conversion problems can be attempted. With a basic knowledge of how many meters make up a kilometer and so forth, metric conversions can be a simple and successful unit for most students.