Early civilizations like Egypt, Mesopotamia, and Rome developed their own measurement systems based on body parts (cubit, foot) and natural phenomena. The Egyptian royal cubit (~52.4 cm) was one of the first standardized units.

During the Middle Ages, each region had its own units. The English foot, inch, and yard became standardized under royal decrees. Trade between regions was complicated by the lack of universal standards.

France introduced the metric system during the French Revolution, based on natural constants. The meter was defined as one ten-millionth of the distance from the equator to the North Pole.

The British Weights and Measures Act standardized the Imperial system, defining the gallon, pound, and other units. This system spread throughout the British Empire.

The 11th General Conference on Weights and Measures established SI as the modern metric system. It defined seven base units: meter, kilogram, second, ampere, kelvin, mole, and candela.

All SI base units were redefined in terms of fundamental physical constants. The kilogram is now based on Planck's constant, ending its reliance on a physical artifact.