Back in 1790, shortly after their famous political revolution, the French National Assembly decided that France also needed to revolutionize its confusing system of weights and measures. A new basic unit of measure was chosen, based on something far more stable than the size of men or plants​—the earth itself. It was set at 1/10,000,000 of the distance between earth’s equator and the North Pole, and was called the meter (39.37 inches). Units of area, weight and volume were derived directly from the meter. Unit values were multiplied or divided merely by adding certain prefixes to the basic unit names.

In 1799, when the system finally became a fact for France, it was given the motto: “For all people, for all time.”

What makes the metric system so superior? Why does even a commercial giant like the U.S., whose changeover costs will be huge, make such a change? If you do not already know the answers, you will find the chart at the right helpful. It shows how much simpler the metric system is.

Instead of over twenty-five different unit names, there are just three basic units, with prefixes, in the metric system! The same set of prefixes is used with all three units. The Greek prefixes deca-, hecto- and kilo- increase the units in multiples of ten, and the Latin prefixes deci-, centi- and milli- reduce them by submultiples of ten, as in the decimal system. Note how this is done, as shown in the chart below.

The prefixes hecto-, deca- and deci- are seldom used, so you can get along quite well by learning just the three basic units and three of the prefixes. For scientific and technical work, eight additional prefixes carry the base unit values up and down much further.

Instead of using inches, feet and miles to measure short, medium and long distances, all metric lengths are expressed in meters with the appropriate prefix: centimeters instead of inches, meters instead of feet or yards, and kilometers instead of miles.

Once the length of the meter and its decimal method of scaling up and down were set, the units of weight and volume were derived from it. A cube one centimeter on each edge became the milliliter 1/1,000 of the basic volume unit, the liter. The gram became the weight of this same milliliter filled with water!

Using the System

Not only is the metric system easier to learn, but it is also easier for most to use than the customary system. Fractions are almost eliminated in the metric system. Since every metric unit is a decimal value of those above and below it, most changes between units require only the moving of a decimal point. For example, to convert kilometers to meters just move the decimal point three places to the right, which automatically multiplies it by 1,000: 3.74 kilometers = 3,740 meters.

By contrast, to find the number of yards in 3.74 miles requires first knowing that there are 1,760 yards in a mile, and then multiplying that figure to arrive at 6,582.4 yards​—no small job if you don’t have a calculator handy. A U.S. Department of Commerce publication notes that “one authority is convinced that the U.S. aerospace industry alone would save about $65 million a year in engineers’ time by converting entirely to metric.”

At the supermarket, thrifty shoppers who compare prices will find that they need not convert pounds to ounces (16) or quarts to ounces (32) before dividing into the price to determine price per ounce. The metric weight or volume can be divided directly into the price in each case.