I like to watch those YouTube videos about tiny houses and interior design. Being French, every time they talk square feet, I have to use Google to convert the dimensions. You know when the ones behind the videos are not Americans when they put the dimensions of the houses in feet and meters. This led me to search for the origin of the metric system.

## Who Invented the Metric System?

First of all, the metric system is now part of the* International System of Units* (like the kilogram, the ampere, the Kelvin, and a lot more units). It means that most of the world used it (unlike the United States customary units that preferred the yard to the meter). Second, the definition:

*a decimal system of weights and measures based on the meter and on the kilogram.*

The history of the metric system started in Europe. In France, an abbot and scientist named Gabriel Mouton published a book in 1670 titled “*Observationes diametrorum solis et lunae apparentium*” in which he proposed the use of a measurement system based on the circumference of the Earth, divided decimally. The idea came from the work of Italian astronomer (and Catholic priest) Giovanni Battista Riccioli who measured the size of the Earth (321,815 Bologna feet to the degree!). From that, Mouton suggested the adoption of the *milliare*, a unit defined as a minute of arc along a meridian arc, and a system of sub-units, dividing successively by factors of ten.

The idea of a coordinated system of units of measure for length, area, volume, and mass was suggested a little earlier by the English Bishop John Wilkins. But it was Mouton’s work—that he refined over the years—that was adopted in 1795 by the national assembly of France as the new system of weights and measures. Yes, more than a century later, after the Révolution, as a way to introduce a little order in this chaotic world. So, in 1790, the *Académie des sciences *asked five French scientists to study the question and preferred the system that didn’t rely on the sizes of specific objects. Instead, it uses a simple set of units derived from nature—originally the *metre* was one ten-millionth of the distance from the equator to the North Pole, but it’s now defined as the length of the path traveled by light in a vacuum in 1/299 792,458 of a second. Also, the kilogram is the weight of a *litre* of water.

Of course, the metric system didn’t become an overnight success. In fact, Napoleon Bonaparte decided in 1812, as Emperor of the French, to introduce another system of measurement (called “*Mesures usuelles*”). It was used until 1840, when King Louis Philippe I chose to go back to the previous law, requiring that all Frenchmen convert to the metric system. During that period, other countries adopted the system—first the Republic of Geneva, Switzerland, in 1813, then the Kingdom of the Netherlands in 1820, the Kingdom of Belgium in 1830, Chile in 1848… In 1885, an *International Association for Obtaining a Uniform Decimal System of Measures, Weights, and Coins* was created during the second Statistical Congress in Paris. Standards were established.

### What About the Metric System in the US?

In 1816, a Swiss-American surveyor named Ferdinand Rudolph Hassler became the first Superintendent of the Survey of the Coast. Hassler was trained in Europe, especially in Switzerland, France, and Germany, and had introduced the standard *metre*, making it the unit of length for geodesy in the United States. This contributed to the introduction of the Metric Act of 1866, also known as the Kasson Act. This piece of legislation was used to legally protect the use of the metric system in commerce from lawsuits, but also to provide an official conversion table from U.S. customary units.

In 1875, the *Convention of the Metre* (aka the Metric Convention) established the International Bureau of Weights and Measures, and a treaty signed by 17 countries, including the United States, led to the adoption of metric standards. This was the first step. The last step was the General Conference on Weights and Measures in 1960 during which an extensive revision and simplification of the system was adopted. It is called the* Système international d’unités* (International System of Units).

After that, in 1971, the US Secretary of Commerce recommended that the US change to the predominant use of the metric system. It was a 10-year plan, but the act was amended in 1988, and the metric system became the preferred system of weights and measures for United States trade and commerce. This time, it was in 1992 that the federal agencies had to use the metric system. This didn’t really take and, now, the US is using dual measurements. Some industries fully adopted the International System of Units, others just some part of it. Due to the exportation of US goods around the world, a lot of products are labeled in metric units, but there is still no legislative effort for mass adoption of the universal system in the US.

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You may also be interested in the story behind the invention of the Periodic Table.