# What is the Metric System?

The metric system, also known as the International System of Units, is a system of measurement established around seven base units. The metric system uses prefixes in multiples of ten for easy conversions. Most countries use the metric system as a standard. Only three countries still exclusively use the imperial system for measurement – the United States, Liberia, and Myanmar.

## The History of the Metric System

France adopted the metric system in 1795. Before then, there weren’t consistent measurements. Instead, the number of choices for weighing, measuring length, and determining volume was too vast.

During the French Revolution, leaders realized how impractical their system was and decided to streamline a new system around natural principles and the power of ten. John Wilkins and Gabriel Mouton played a significant role in creating the metric measuring system by basing measurements on the meter and kilogram with decimal values.

They based metric systems measurements on natural and practical applications. For example, Wilkins and Mouton based original length measurements off a pendulum and, later, the length of the Earth. They based mass on one liter of water.

During the mid-19th century, Scottish mathematician, James Clerk Maxwell, proposed smaller based units for length, mass, and time to make measuring simple. He called other units of measure derived units. In 1901, a base unit to measure electromagnetism was also introduced.

## The Creation of the International System of Units (SI)

In 1960, the General Conference on Weights and Measurements established the modern metric system.

The system, known as the International System of Units (SI), labeled six base units – meter for length, second for time, kilogram for mass, ampere for electrical current, kelvin for thermodynamic temperature, and candela for luminous intensity. Later, they added the mole as the seventh unit for measuring an amount of substance.

## What is in the Metric System: Base Units

The seven metric system base units measure different aspects, each with its own symbol.

Here’s a look at the base units of the metric system:

UnitSymbolMeasure
Metermlength
Secondstime
KilogramKgmass
AmpereAelectrical current
KelvinKthermodynamic temperature
Molemolamount of a substance
Candelacdluminous intensity

Aside from base units, there are also derived units in the metric system. A derived unit is a mathematical combination of base units. For example, the square meter, a measurement of area, is a derived unit (m*m) that measures area. Degrees Celsius is also considered a derived unit from the base unit Kelvin.

## Common Metric System Unit for Measuring Length, Weight, Area, and Volume

Some common units measure length, weight, area, and volume.

• Metric system units for measuring length are derived from the meter. These include the millimeter, centimeter, meter, and kilometer.
• Metric system units for measuring weight or mass are the gram, kilogram, tonne, milligram, and centigram.
• Metric system units for measuring area include square meters, square centimeters, and hectares.
• Metric system units for measuring volume include liters, milliliters, centiliters, and kiloliters.

## Metric System Prefixes

To make measuring and converting easy, the metric system uses prefixes. So, for example, instead of saying an object measures 1,000 meters, you can say it’s a kilometer. The prefix “kilo” means 1,000. So 1 kilometer is the same as 1,000 meters. Likewise, the prefix “centi” means one-one hundred, making the centimeter 1/100th of a meter.

Here’s a table showing the six most common metric system prefixes, according to the National Institute of Standards and Technology.

PrefixSymbolValue
Kilok1,000
Hectoh100
Decid0.1
Centic0.01
Millim0.001

## Imperial System vs. Metric System

The British Imperial system originates from the UK. It’s similar to the United States Customary System for measuring. The British Imperial and United States Customary systems use units such as the foot, inch, mile, pound, and gallon.

Unlike metric measurements, the Imperial system doesn’t use decimals; therefore, there are no specific conversion units. As a result, it’s more complicated to convert imperial measurements than it is to convert metric units.

## Why Doesn’t the United States Use the Metric System?

The US established the United States Customary System in 1832 before the metric system was as common. At the time, country leaders based their weights and measurements on English measurements from the British Imperial System.

One big reason the United States doesn’t switch to the metric system is the expense. Converting measurements, especially in factory and manufacturing settings, would be a cost most businesses can’t absorb. In addition to converting all current measurements, the US would need to educate residents on a new system.