There are two systems of measurement in the world – the metric system and the imperial system.

These days, the metric system is known as the International System of Units (SI), a universal system of measurement used in almost every country in the world.

It was created over two centuries ago and, in that time, has gone through various changes to make it what it is today.

To take a trip down memory lane, we’ve created this article to explore the history of the metric system, such as when it was invented, why it was adopted internationally, and how it became known as the International System of Units.

Five French scientists invented the metric system. At the time, it was called the ‘decimal metric system’ and became the first iteration of the metric system we know today.

The metric system was officially invented on 30 March 1791 when the French Assembly accepted a proposal for a uniform standard of weights and measures. Once accepted, the French Assembly slowly implemented this proposal throughout the entire nation.

However, it wasn't until 7 April 1795 that it was passed into French Law. This new system became the first iteration of the metric system and had the following unit definitions:

  • Mètre (meter) – This was the unit of measurement for length. It was defined as one ten-millionth of the distance between the equator and the North Pole when measured through Paris.
  • Are (hectare) – This was the unit of measurement for an area of land. It was defined as one hundred meters squared (100 m2).
  • Litre (liter) – This was the unit of measurement for volumes of liquid. It was defined as one cubic decimeter (1 dm3).
  • Gramme (gram) – This was the unit of measurement for mass. It was defined as one cubic centimeter of water.
  • Franc – This was the unit of measurement for currency
  • Stère – This was the unit of measurement for volumes of firewood. It was defined as one cubic meter (1 m3).

Although this was the first time that the coherent system of metric measurements was put together, the idea wasn’t new. In fact, it had been talked about for centuries before.

Prior to the standardized metric system, not only did measurement systems differ between countries, but they also differed within them. Units of length, weight, land, volume, etc., would vary between regions and also between locals. For example, France alone had almost 800 different units of weights and measures that would vary from town to town and between different professions.

A few measurements were recognized nationwide, such as the King’s foot, which was used in scientific and engineering work. Still, many traders and locals preferred to use their own measurement scales on a daily basis. While this may have worked on a small scale, it was incredibly inefficient.

After the start of the French Revolution in the late 1780s and early 1790s, this inefficiency became glaringly apparent to scientists and scholars as they could not facilitate trade and determine taxation amounts on a mass scale. This led to a growing need for standard units of measurement that would work throughout the country and internationally. As such, five scientists were tasked with creating a rational system in 1790.

Once this was passed into law in 1975, it officially became the preferred measurement system in France for a short period.

Although France passed the metric units into law, the general population was slow to come around. They preferred to use their existing units of measurement, something they had been using for generations prior. In fact, it was disliked so much that Napoleon revoked the law in 1812.

But after the fall of his empire, the new National Assembly reintroduced the metric system in 1837. What was planned to be a three-year process took 11 years and was only completed in 1858.

However, between that period, the Benelux countries of Belgium, Netherlands, and Luxembourg officially adopted the metric system in 1820, making them the first countries to do so.

There was a huge movement amongst scholars, engineers, scientists, and businessmen around the time that Belgium, Netherlands, Luxembourg, and France adopted the metric system. This was partly due to the success of seeing national standards in practice. But, it was also because of the ability to trade and communicate internationally.

Seeing this led to a growing sentiment for a universal system. At the time, countries only had the British Imperial system or the metric system to choose from. The British Imperial system was closely linked to the British Empire, which meant countries were opposed to that option. This left them with no other choice but to adopt metric.

It grew rapidly across the 19th century and became the sole measurement system for most of Latin America and mainland Europe. As such, it also became the primary measurement used in science. Its widespread use continued all the way into the 20th century when its most recent iteration occurred.

The International System of Units (SI) is a metric and decimal system of units. It is the modern metric system as we know it today and has official status in almost every country worldwide. It is overseen by the International Bureau of Weights and Measures (IBWM), an organization that consists of 59 member states.

When was the International System of Units created?

The International System of Units was created in 1960. After World War 2, there was a growing need for international cooperation, and we saw the creation of numerous international organizations, such as the World Health Organization and the United Nations. Part of that movement was the creation of international units of measurement, now known as SI.

Metric systems of measurement as used in all but three countries in the world – the USA, Liberia, and Myanmar. Officially these countries still use the imperial system. However, it should be noted that in day-to-day uses, the USA has a hybrid system of both imperial and metric. For instance, kilometers are the unit of measurement for distance instead of miles.

Base units are the seven standard units of measurement recognized by the International System of Units. Some of them are the same as when the metric system was first invented back in 1795, but there are some new additions. They are as follows:

Base Units

Base unitLengthmeterm
Areasquare metersquare m, or m2
Areaare (100 square meters)a
Volumecubic metercubic m, or m3
Volumestere (1 cubic meter)s
Weightmetric ton (1,000,000 grams)t
Temperaturedegree Celsius°C

What makes the metric system so easy to follow is that all the basic units are expressed with a prefix. The prefix will determine the multiple or submultiple of the unit – i.e., how big or small – which can be used to measure the exact quantity. Let’s take a look at them below.


PrefixSymbolFactor by which to multiply the base unitName
Whole units (larger quantities)yotta-Y1024Septillion
hecto-, hect-h102Hundred
deca-, dec-da101Ten

Sub-units (smaller quantites)deci-d10−1Tenth
centi-, cent-c10−2Hundredth
micro-, micr-μ10−6Millionth


The metric system was invented and officially passed into French law in 1795. It arose from a need to standardize measurements across the country and abroad, which was proving challenging. Some of the basic units, such as meter, liter, and grams, are still used to this day, but there are some new additions, such as the metric tonne.

Although it isn’t officially adopted in every country, it’s the most widely used measurement system in the world and is used in science and engineering.