In the U.S., miles mark the distance on a road trip. Cups measure ingredients for baking, and inches show how tall you’ve grown. These measures, known as U.S. customary units, are part of the imperial system of measurement.
But most countries use the metric system, which includes units such as meters, liters, and grams. In fact, the U.S. is one of only three countries that hasn’t adopted the metric system. In 1975, Congress passed the Metric Conversion Act to try to get Americans to make the switch, but the metric system has never fully caught on.
Some people say it’s time for a change. They point out that metric units are used in fields such as science and medicine. They also note that the metric system is less confusing because it is based on units of 10. For example, 1,000 grams equals 1 kilogram. In the U.S. system, 16 ounces equals 1 pound.
But others argue that it would be difficult for an entire country to learn a new way to measure.