Traditional French units of measurement

The traditional French units of measurement prior to metrication were established under Charlemagne during the Carolingian Renaissance.

The change was extremely unpopular, however, and a metricized version of the traditional units—the mesures usuelles—had to be brought back into use for several decades.

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.

[2] 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.

[6] The loi du 19 frimaire an VIII (Law of 10 December 1799) states that one decimal metre is exactly 443.296 French lines, or 3 pieds 11.296 lignes de la "Toise du Pérou".

[14] Jean II (1319–1364) constructed a new standard of measures, including a livre actuelle ("current" pound, also known as a livre de poids de marc or "mark weight" pound) of 2 marcs, i.e. 16 onces.

[22] Jean II's standards are preserved in the Conservatoire Nationale des Arts et Métiers, which also holds a set of later-still physical standards from the 15th century, the so-called pile de Charlemagne.

[25] The thirteen individual pieces that made up the Parisian pile de Charlemagne comprised an outer containing cylinder nominally weighing 20 marcs, and a set of hollow nesting cups within, topped with a filled weight as the smallest piece.

[24] Louis Lefèvre‑Gineau initially determined that the metric weight of the whole pile was 12.227 947 5 kg,[28] later corrected to 12.2376 kg,[29] thereby making (by division and rounded to three decimal places) a marc 244.753 g, a livre esterlin 367.129 g, and a livre actuelle 489.506 g.[20][30] Hence further the (Parisian) once was 30.594 g, the gros/drachme was 3.824 g, the denier/scruple was 1.274 g, and the grain was 0.053 g.[19][16] However, the actual weights of the pre-metric measures were nowhere near even this simple.

[31] For just some examples: the Marseille livre was 399.6 g, the Montpelier one 394.9 g, the Toulon one 465.5 g, and the Toulouse one 413.2 g; with all of the fractional subdivisions having different values accordingly.