Scientists all over the world use the metric system. There’s a very good reason for this—it’s so everyone is doing the measuring the same way, all over the world. Most other countries already use the metric system for measuring everything.
Another good reason to use metric is that you don’t have so much to remember—no 12 inches in a foot or 5,280 feet in a mile. It’s all decimal! The larger or smaller units go up or down by 10, 100, or 1,000.
Meter is for length. A meter is a little longer than a yard. For long distances, there is the kilometer (a thousand meters). For small things, there is the centimeter (100 centimeters in a meter).
Liter is for volume. A liter is a little larger than a quart. There are a thousand milliliters in a liter.
Gram is for weight. A gram is a little more than the weight of a paper clip. For heavier things, there is the kilogram (a thousand grams).
Temperatures are in degrees Celsius (also called centigrade). Water freezes at 0 degrees Celsius and boils at 100 degrees Celsius. That’s easy!