Metric and Imperial Unit Converters and Conversion Tables

People have been measuring things for thousands of years.Ancient Egyptians used fingers, hands and arms to measure things. One finger is a digit, 4 fingers a palm, the distance between their elbow to the fingers is a cubit etc. All these units of measurement were based on something familiar to them, such as their body parts, but even the results varied from person to person. Almost all countries or cultures used different units of measurement and conversion of units within or between the same systems has become a problem. There was no agreed upon standard of measurement.

Imperial System:

The Imperial system is derived from the old English units which evolved from the hundreds of Roman, Celtic and Anglo-Saxon units used in history. English units were used until 1824 and then the official imperial system was defined by the British Weights and Measures Act as the standard measurement system in Britain and in commonwealth countries. Within years, the units were refined and reduced. In 1965, the metric system was adopted but still several common units are being used in everyday life (foot, inch, mile etc).

US Customary System:

US Customary system is the measurement system used in the United States and a few Caribbean countries. It's derived from the old English measurement system similar to the imperial system, but it was used in the United States before the imperial system was defined in 1824, that's why most of the measurement unit names are the same but the values might be slightly different, especially for the weight and volume units. In 1832, it was officially accepted to be used by customs officials at US ports and missed the opportunity to adopt the Metric system (originated in 1790 in France) as early as the 19th century. Later, in 1893, many units were redefined in terms of meter and kilogram (imported from metric system) and redefined again in 1959 by the international yard and pound agreement between six nations (US, UK, Canada, Australia, New Zealand and South Africa) so that the yard is redefined to be as exactly 0.9144 meter and the pound as exactly 0.45359237 kilogram. Metrication in the US is not officially enforced, unlike the other nations. US Customary units are commonly used in everyday life but for science, military and medicine, metric units are mostly used.

Metric System:

Metric system is a decimalized measurement system created in 1790 during the French revolution for the purpose of creating a measurement system for everybody. The base length unit was the metre (the definition was replaced later in 1983), the volume unit was litre (one thousandth of a cubic metre) and the unit of mass was the kilogram (mass of one litre of water). The kilogram and metre prototypes were kept by French government until 1875. In 1875, Metre Convention (Treaty of the Metre) was signed by the 17 countries for the purpose of administering the maintenance and the development of metric standards globally. Three international organizations were born. They are the General Conference on Weights and Measures (decision making organization, meets every 4-6 years to discuss the new developments in the Metric system), International Committee for Weights and Measures (18 high scientific standing individuals from member countries to advise on technical matters) and BIPM (International Bureau of Weights and Measures to ensure the uniformity of metric weights and measures around the world). After 1875, the prototypes are kept at the office of BIPM in France.

The unit names are based on adding the prefixes "centi", "kilo' etc as decimal multipliers, which makes the Metric system very easy compared to the other measurement systems, since to convert between the units, all you have to do is to multiply by a decimal. For example, to calculate how many centimeters in a meter, all you have to do is multiply it by 100 since "centi" denotes a factor of one hundredth in metric system. In imperial or US Customary, to calculate how many inches in a mile, you must know how many inches in a foot, then how many feet in a mile and then multiply these two results to find your answer which is a kind of a difficulty for many people.

SI - International System of Units:

Metric system was based on the metre and kilogram standards, but was not enough for all types of physics measurements, so 1960 SI (International System of Units) was born. It is an evolving measurement system which means the units are redefined as needed and new ones added. SI is the world's mostly used measurement system, adopted globally except United States, Burma and Liberia.

There are seven base units in SI system. They are metre for length, kilogram for mass, second for time, ampere for electric current, kelvin for temperature, candela for luminous intensity and mole for amount of substance. All the other units are based on these units and they are called derived units.

For more information about these measurement systems, visit links