Metric system Crossword Puzzle for Kids

The metric system is a number of different systems of measurement with length based on the metre, mass on the gram, and volume on the litre. This system is used around the world. It was developed in France and first introduced there in 1795, 2 years after the execution of Louis XVI. The metric units are based on decimal groups (multiples of ten). At first the metric system was based on two quantities: length and weight. The basic units were called the metre and the gramme.

In 1866, the United States started to use the metric system, and is widely used except by the public. By 1875, many countries in Europe and in Latin America had changed to using the metric system. In 1875, seventeen countries signed the Metre Convention agreeing to share responsibility for defining and managing the metre and kilogram standards. The prototype copies of the metre and of the kilogram were called the "international prototype metre" and "international prototype kilogram". A new organization called the International Bureau of Weights and Measures (BIPM) was set up. The international prototype metre and kilogram were kept at the BIPM headquarters. In 1960, the rules for the metric system were revised. The revised system was called the "International System of Units" (which is often called "SI" for short). The definition of SI also included rules for writing SI quantities. These rules are the same for all countries. In the 1970s, many people in the United Kingdom and the rest of the Commonwealth started using the metric system in their places of work.

Description

The metric system is a decimal-based system of measurement. The system has units of measure for each quantity. The names of most units of measure in the metric system have two parts. One part is the unit name and the other part is the prefix. For example, in the name "centimetre", the word "centi" is the prefix and the word "metre" is the unit name. Sometimes, as with metre, litre and gram, there is no prefix.

In the metric system, all units have a "symbol". Symbols are a shorthand way of writing the names of units. All the countries in the world use the same symbol for a unit, even though they might have different ways of writing out the unit name in full. For example

The metric system was first developed in France during the French Revolution. A French law passed in 1795 defined five units of measure. Three of these names are still in use today. They are the metre which is the unit of length, the gram which is the unit of mass and the litre which is the unit of volume. Since then many other units of measure have been developed and many definitions changed. The metric system now has units of measurement for energy, power, force, electric current, radioactivity and many others. The most commonly used units of measure in the metric system are listed below.

In the metric system, length is measured in metres. The symbol for the metre is the letter "m". The metre was originally defined as being 1/10,000,000 of the distance between the North Pole and the Equator on the meridian that passed through Paris. In 1799, a platinum bar that was equal to this length was made and became the "prototype metre"

In the metric system, volume is measured in litres. The symbol for the litre is "L". In 1795 the French Government defined one litre as being the same volume as the volume of a cube which had sides that were 10 cm.

How big

These tables will help one to estimate the size of different lengths or masses in the metric system. In these tables:

The word "Imperial" is short for Imperial units which are the units of measure that have traditionally been used in the United Kingdom.

The word "Customary" is short for U.S. customary units which are units of measure that have traditionally been used in the United States.

British and American spelling

Some names in the metric system are spelt differently in British English and in American English and Philippine English.

The word metre is used in British English while the word meter is used in American English.

The word litre is used in British English while the word liter is used in American English.

The word gram is used in both British English and in American English. The word gramme can also be used in British English, but many British people think that this is old-fashioned.

Administering the metric system

In 1875 representatives from the governments of twenty different countries met in Paris to discuss weights and measures. Seventeen of the countries signed a treaty about weights and measures. The treaty was called "The Convention of the Metre". The countries that signed were: Argentine Confederation, Austria-Hungary, Belgium, Brazil, Denmark, France, Germany, Italy, Peru, Portugal, Russia, Spain, Sweden and Norway, Switzerland, Turkey, United States and Venezuela. They agreed:

To set up an inter-governmental organisation to administer the treaty. This organization was called the International Bureau of Weights and Measures (BIPM).

France was to have responsibility for acquiring suitable premises for the BIPM. These premises would become neutral territory. The BIPM offices and laboratories would be located on the site.

To make 40 identical copies of the kilogram. One was chosen as the prototype (or primary) copy. This copy was known as the "International Prototype Kilogram". It replaced the Kilogramme des archives as the world's primary copy of the kilogram. The Kilogramme des archives would be kept at the BIPM premises.

To make 30 identical copies of the metre. One was chosen as the prototype (or primary) copy. This copy was known as the "International Prototype Metre". It replaced the Metre des archives as the world's primary copy of the metre. The Metre des archives would be kept at the BIPM premises.

History

There are 16 US fluid ounces in a US pint but there are 20 imperial [UK] fluid ounces in an imperial pint. The US fluid ounce is larger than the imperial fluid ounce, but the imperial pint is larger than the US pint. In the 1700's this type situation was common across Europe. Each country measured length, weight/mass and volume in its own way. Sometimes different countries or cities used the same name for different measurements. Sometimes different cities in the same country had different ways of measuring things. In 1789 there were a quarter of a million different units of weight and measure in France.

During the French Revolution, French scientists decided that it would be better to have a new system of weights and measures. The system would be the same in all French provinces and cities. They also decided that it would be easier if the new system used 10's instead of 12's, 16's or 20's, because people normally count in 10's. The new system became the official system of measurement in France in 1799. One of the French leaders, the Marquis de Condorcet declared that "[the metric system] is for all people for all time".

They decided that the new system would be for everybody on Earth and that the new unit of length would be called a "metre". They decided there would be 10000 km between the North Pole and the equator. Between 1791 and 1798 two surveyors, Pierre Méchain and Jean-Baptiste Delambre, measured the distance between the cities of Dunkirk to Barcelona using old French units, and used the stars to measure their latitudes. They used this information to work out that the length of the metre should be 443.296 lignes. In 1798 the French scientists made a bar of platinum that was exactly one metre long. They stored this bar in the French archives. It was called the metre des archives. People who made one metre rulers were able to check that their rulers were the same length as the metre des archives. Other scientists made a kilogram weight from platinum which was also put in the archives. This weight was called the kilogram des archives.

In 1799 the metric system was made compulsory, meaning people were made to use it by law, in the region around Paris. This caused a lot of confusion because the police enforced the new measures but customers preferred the old ones. So shopkeepers had to have both. People became worried the new measures were used to cheat them. Politicians tried to educate and convince people to use metric, but the people rejected the metric system. In 1800 the government tried to make the system acceptable by changing the names of the units back to the simpler names used before metrication. For example, the decimetre, centimetre, and millimetre were renamed to palme (hand), doigt (finger) and trait (trace).

In 1799 Napoleon became the leader of France. By 1812 he had conquered most of Europe. He introduced the metric system to the countries that he conquered. In 1815 he was defeated at the Battle of Waterloo. After Napoleon was defeated, most of the countries started using their old systems of measurement again.

Related pages

International System of Units, describes more advanced aspects of the metric system

Text adapted from the Simple English Wikipedia article “Metric system” (revision 10737737, 2026-02-03), authors, licensed under CC BY-SA 4.0.