Why in the world do we need weights and measures?

There are two main systems of measurement in the world:  the U.S. Customary System and the International (Metric) System:

The U.S. Customary System is the system used in the United States. It measures length in inches, feet, yards and miles.  It measures weight in ounces, pounds and tons, and volume in pints, quarts and gallons.   The U.S. Customary System is very similar to the system the colonists brought from England.  Much of the system can be traced back to early Babylonian, Eqyptian and Roman cultures.

The International (Metric) System,   known as SI, is used in most of the world.  It is also used for almost all scientific work. A metric system was first proposed in France in 1670.  France adopted the metric standard in 1840 and many countries followed.  Today, the only developed nations which do not use the SI metric system are the United States, Liberia and Burma.

There are three basic units in the metric system:  meter, liter and gram.  
The meter measures length.  The liter measures volume, and the gram is a measurement for mass or weight. 

Is it confusing to have two systems of measurement in the world?

It would be much easier to have one standard system throughout the world.  The metric system has been adopted by most countries because it is an easy system to use.   Everything is based on the number ten.  This is called a decimal system.   Basically, all you need to do in order to change numbers to larger or smaller units is multiply or divide them by ten.  With the U.S. Customary System, we must multiply and divide by numbers like 16, because there are 16 ounces in a pound, or 12 because there are 12 inches in a foot, or 32 fluid ounces in a quart. 

Will the United States ever adopt the SI and become metric like the rest of the world?

The U.S. has actually recognized the metric system since the early 1800s.  In 1866, Congress authorized the use of the metric system in this country and supplied each state with a set of metric weights and volumetric measures.  In 1975, the Metric Conversion Act was passed in the U.S. to coordinate greater use of the metric system.

The U.S. realized that it was very difficult for its industries to compete in a metric world.  Other countries such as Japan, Britain and Germany were shipping products all over the world.  It was difficult for the U.S. to compete because the standards were different and everything had to be converted to metric.  Congress knew we had to change to the international standards for trade.  In 1988, a trade act was adopted that made the metric system the preferred system of measurement for trade and commerce.   It also required that all Federal agencies do business using the metric system.   This did not do away with the U.S. Customary System, but it did make metric equally important.

Although you may not realize it, you deal with metrics every day.  A two liter bottle of soda pop is common in our grocery stores.  International sporting events such as track and field and swimming races measure distance in meters.  Remember reading about the gram?  This measurement is used in most laboratories and in the medical field.  You can also see it on packaged products we purchase in grocery and other retail stores.