Traditional French units of measurement

Before the French Revolution, which started in 1789, French units of measurement were based on the Carolingian system, introduced by the first Holy Roman Emperor Charlemagne (800 – 814 AD) which in turn were based on ancient Roman measures. Charlemagne brought a consistent system of measures across the entire empire. However, after his death, the empire fragmented and many rulers introduced their own variants of the units of measure.

Some of Charlemagne's units of measure, such as the pied du Roi (the king's foot) remained virtually unchanged for about a thousand years, while others, such as the aune (ell—used to measure cloth) and the livre (pound) varied dramatically from locality to locality. By the time of the revolution, the number of units of measure had grown to the extent that it was almost impossible to keep track of them.

Although the pre-revolutionary era (before 1795) when France used a system of measures that had many of the characteristics of the Imperial System of units, there was no unified system of measurement in France. Whereas in England the Magna Carta decreed that "there shall be one unit of measure throughout the realm", Charlemagne and successive kings had tried but failed to impose a unified system of measurement in France.

The names and relationships of many units of measure were adopted from Roman units of measure and much more were added – it has been estimated that there were seven or eight hundred different names for the various units of measure. Moreover, the quantity associated with each unit of measure differed from town to town and even from trade to trade to the extent that the lieu (league) could vary from 3.268  km in Beauce to 5.849  km in Provence. It has been estimated that on the eve of the Revolution a quarter of a million different units of measure were in use in France. Although certain standards, such as the pied du Roi (the King's foot) had a degree of pre-eminence and were used by savants, many traders chose to use their own measuring devices giving scope for fraud and hindering commerce and industry.

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