## What is metrication?

Metrication is the process of switching from the use of an incoherent collection of countless historical and parochial weights and measures to the use of a single, coherent, standard system of weights and measures known as the metric system.

More recently, it has come to refer more specifically to the process of converting to the use of the modern iteration of the metric system – the International System of Units (SI).

Since its initial development in the 1790s, the metric system has become the world’s standard system of weights and measures.

Every country in the world has adopted the metric system for some or all official purposes. However, while most countries have now completed metrication, a few, including the UK, have yet to adopt the metric system for all official purposes.

In those few countries where old measurement units continue to be used, such as yards and miles on British road signs, the old units are now legally defined in terms of metric units. Thus, for most purposes, the metre is not permitted to be used on UK road signs to indicate distance, unless it is shown in multiples of 0.9144 m, and labelled as “yards”. (One yard is defined as 0.9144 m).

## What is the metric system?

Officially known as the International System of Units (SI), the metric system is the international standard system of measurement. It is based on the standard decimal number system, and is designed to be easy to learn, and simple to use.

In everyday use, it is used to measure road distances and speeds, floor areas, storage volumes, energy use, and the mass and volumes of food and drink.

It is also used to measure temperature, electricity and the brightness of light bulbs. It is the standard system of measurement for all trade.

Units of measurement in the metric system relate to each other in a logical and coherent manner. Each quantity has one unit to measure it. Standard metric prefixes can be combined with any metric unit to form subunits which are multiples or submultiples of 10. All calculations using metric units are as straight forward as any other calculation using decimal numbers.

The metric system is based on properties of nature:

- The distance from the North Pole to the Equator is 10 million metres, or 10 000 kilometres.
- 1 metre can be divided into 10 decimetres, 100 centimetres or 1000 millimetres.
- 1 m = 10 dm = 100 cm = 1000 mm.
- 1 litre is the volume of a cube with sides of length 1 dm, or 10 cm.
- 1 kilogram is the mass of 1 litre of water.
- Water freezes at 0 degrees Celsius, and boils at 100 degrees Celsius.

Since its original inception, the metric system has evolved to become a single coherent system used for measurement in all fields of human endeavour, including science, medicine, technology, industry, commerce and sport.