- In 1585, Simon Stevin proposed using a decimal system for measuring weight, distance and currency, but it wasn't until around 1670 that Gabriel Mouton created a functioning system. Though Thomas Jefferson suggested the U.S. adopt a metric system in 1790, it was French Academy of Sciences that first studied it that year, which led to France adopting it in 1795.
- Napoleon discontinued the use of the metric system in 1812, but it was re-instituted in 1840. In 1875, 17 countries signed "The Convention of the Metre" and by 1900, 35 countries had officially adopted the metric system. Even though the United States still used the English system, English units were officially based on metric measurements.
- The metric system is easier to use than the English system because it uses base units and then powers of 10, so you can simply shift the decimal point; the English system uses different conversion factors like 12 inches to a foot and three feet to a yard. The metric system uses prefixes to denote the relationship of the base unit to the unit in use. For example, a kilometer is equivalent to 1,000 meters and a kilogram is equal to 1,000 grams.
- Most metric system units have been adopted into the International System of Units used for international measurement. There are six base metric units--meter, kilogram, second, ampere, mole and candela--in addition the kelvin for temperature.
- The only major country that has not officially adopted the metric system is the United States. In 1975, the U.S. passed the Metric Conversion Act, which called for the country to voluntarily convert, but there was no timetable in the final bill. Since then, a number of groups--including some large industries--have converted to metric measurement--but no official change has been made. When U.S. companies ship overseas, they have to label their packages with metric units. By the end of 2009, the United States should allow only metric packaging.