Units of measurement in France before the French Revolution

Woodcut dated 1800 illustrating the new decimal units which became the legal norm across all France on 4 November 1800

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.

History

Table of the measuring units used in the 17th century at Pernes-les-Fontaines in the covered market at Provence-Alpes-Côte d'Azur region of southeastern France

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.^[1]

The names and relationships of many units of measure were adopted from Roman units of measure and many 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 lieue (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.^[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.^[1]

As an example, the weights and measures used at Pernes-les-Fontaines in south eastern France differ from those catalogued later in this article as having been used in Paris. In many cases the names are different, while the livre is shown as being 403 g, as opposed to 489 g - the value of the livre du roi.

Tables of units of measure

17th Century engraving of the Grand Châtelet

Flood levels at the pont Wilson at Tours in both metres and pied royal

These definitions use the Paris definitions for the coutume of Paris,^[3] and definitions for other Ancien régime civil jurisdictions varied, at times quite significantly.

Length

The mediaeval royal units of length were based on the toise and in particular the toise de l'Écritoire, the distance between the fingertips of the outstretched arms of a man which was introduced in 790 AD by Charlemagne.^[4] The toise has 6 pied (feet) each of 326.6 mm (12.86 in). In 1668 the reference standard was found to have been deformed and it was replaced by the toise du Châtelet which, to accommodate the deformation of the earlier standard, was 11 mm (0.55%) shorter.^[5] In 1747 this toise was replaced by a new toise of near-identical length - the Toise du Pérou, custody of which was given to l'Académie des Sciences au Louvre.^[6]

Although the pouce (inch), pied (foot) and toise (fathom) were fairly consistent throughout most of pre-revolutionary France, some areas had local variants of the toise. Other units of measure such as the aune (ell), the perche (perch/rood), the arpent and the lieue (league) had a number of variations, particularly the aune (which was used to measure cloth^[7]

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".^[8] Thus the French royal foot is exactly 9000/27706 metres ( about 0.3248 m).^[9]

In Quebec, the surveys in French units were converted using the relationship 1 pied (of the French variety, the same word being used for English feet as well) = 12.789 English inches.^[10] This makes the Quebec pied very slightly smaller (about 4 parts in one million) than the pied used in France.

Table of length units
Unit	Relative value	SI value	Imperial value	Notes
point	1/12^3	~0.188 mm	~7.401 thou	This unit is usually called the Truchet point in English.
ligne	1/12^2	~2.256 mm	~88.81 thou	This corresponds to the line, a traditional English unit.
pouce	1/12	~27.07 mm	~1.066 in	This corresponds to the inch, a traditional English unit.
pied du roi	1	~32.48 cm	~1.066 ft	Commonly abbreviated to 'Pied', this corresponds to the foot, a traditional English unit. Known in English as the Paris foot (properly a separate, shorter unit), the royal foot, or French foot.
toise	6	~1.949 m	~6.394 ft, or ~2.131 yd	This corresponds to the fathom, a traditional English unit. Unlike the fathom, it was used in both land and sea contexts.
Paris
perche d'arpent	22	~7.146 m	~7.815 yd
arpent	220	~71.46 m	~78.15 yd
lieue ancienne	10,000	~3.248 km	~2.018 miles	This is an old French league, defined as 10,000 (a myriad) feet. It was the official league in parts of France until 1674.
lieue de Paris	12,000	~3.898 km	~2.422 miles	This league was defined in 1674 as exactly 2000 toises. After 1737, it was also called the "league of bridges and roads" (des Ponts et des Chaussées).
lieue des Postes	13,200	~4.288 km	~2.664 miles	This league is 2200 toises. It was created in 1737.
lieue de 25 au degré	~13,692	~4.448 km	~2.764 miles	Linked to the circumference of the Earth, with 25 lieues making up one degree of a great circle. It was measured by Picard in 1669 to be 2282 toises.
lieue tarifaire	14,400	~4.678 km	~2.907 miles	This league is 2400 toises. It was created in 1737.
North America
perche du roi	18	~5.847 m	~6.394 yd	This perch was used in Quebec and Louisiana
arpent	180	~58.47 m	~63.94 yd
Local
perche ordinaire	20	~6.497 m	~7.105 yd	This perch was used locally.
arpent	200	~64.97 m	~71.05 yd

• The French typographic point, the Didot point, was 1/72 French inches, i.e. two royal points. The French pica, called Cicéro, measured 12 Didot points.

Area

Table of area units
Unit	Relative value	SI value	Imperial value	Notes
pied carré	1	~1055 cm^2	~1.136 sq ft	This is the French square foot.
toise carrée	36	~3.799 m^2	~40.889 sq ft, or ~4.543 sq yd	This is the French square fathom.
Paris
perche d'arpent carrée	484	~51.07 m^2	~61.08 sq yd	This was the main square perch in old French surveying. It is a square 22 feet on each side.
vergée	12,100	~1277 m^2	~1527 sq yd	This is a square 5 perches on each side.
acre, or arpent carré	48,400	~5107 m^2	~6108 sq yd, or ~1.262 acres	The French acre is a square 10 perches on each side.
North America
perche du roi carrée	324	~34.19 m^2	~40.89 sq yd	This square perch was used in Quebec and Louisiana. It is a square 18 feet on each side.
vergée	8,100	~854.7 m^2	~1022 sq yd	This is a square 5 perches on each side.
acre, or arpent carré	32,400	~3419 m^2	~4089 sq yd, or ~0.8448 acres	This acre is a square 10 perches on each side. Certain U.S. states have their own official definitions for the (square) arpent, which vary slightly from this value.
Local
perche (ordinaire) carrée	400	~42.21 m^2	~50.48 sq yd	This square perch was used locally. It is a square 20 feet on each side.
vergée	10,000	~1055 m^2	~1262 sq yd	This is a square 5 perches on each side.
acre, or arpent carré	40,000	~4221 m^2	~5048 sq yd, or ~1.043 acres	This acre is a square 10 perches on each side.

Volume - Liquid measures

Table of (liquid) volume units
Unit	Relative value	SI value	U.S. value	Imperial value	Notes
roquille	1/32	~29.75 ml
posson	1/8	~119 ml
demiard	1/4	~238 ml	~1/2 pint		Etymologically, 'demi' in French means 'half', in this case, half a chopine, and - conveniently - also half a (US) pint.
chopine	1/2	~476.1 ml	~1 pint	~0.84 pint
pinte	1	~952.1 ml	~2.01 pint	~1.68 pint	Although etymologically related to the English unit pint, the French pint is about twice as large. It was the main small unit in common use, and measured 1/36 of a cubic French foot.
quade	2	~1.904 L	~1/2 gallon	~0.42 gallon
velte	8	~7.617 L	~2.01 gallon	~1.68 gallon
quartaut	72	~68.55 L			A quartaut is 9 veltes.
feuillette	144	~137.1 L
muid	288	~274.2 L			The muid is defined as eight French cubic feet.
cubic
pouce cube	1/48	~19.84 ml			This is the French cubic inch.
pied cube	36	~34.28 L			This is the French cubic foot. In ancient times, a cubic foot was also known as an amphora when measuring liquid volume.

Volume - Dry measures

Table of (dry) volume units
Unit	Relative value	SI value	imperial value	U.S. value	Notes
litron	^1⁄16	793.5 mL	0.1745 imp gal	0.1801 U.S. dry gal	The litre is etymologically related to this unit.
quart	^1⁄4	3.174 L	0.698 imp gal	0.721 U.S. dry gal
boisseau	1	12.7 L	2.8 imp gal	2.9 U.S. dry gal	A boisseau was defined as ^10⁄27 of a French cubic foot.
minot	3	38.09 L	8.38 imp gal	8.65 U.S. dry gal
mine	6	76.17 L	16.76 imp gal	17.29 U.S. dry gal
setier	12	152.3 L	33.5 imp gal	34.6 U.S. dry gal
muid	144	1,828 L	402 imp gal	415 U.S. dry gal
cubic
pouce cube	^1⁄640	~19.84 cm^3	~1.211 cu in		This is the French cubic inch.
pied cube	2.7	~34.28 dm^3	~2,092 cu in		This is the French cubic foot.

Mass

According to the law of 19 Frimaire An VIII (December 10, 1799),

• The kilogramme is equal to 18,827.15 grains. The kilogramme is, in addition, defined as the weight of 1 dm³ of distilled water at 4 degrees centigrade, i.e. at maximum density.^[6]

Traditionally, the French pound (livre) was defined as the mass of exactly ¹⁄₇₀ of a French cubic foot of water. When the kilogramme was defined, knowledge that a pied du roi cube filled with water masses exactly 70 French pounds was apparently lost. According to the traditional (cubic foot) definition, one livre would have been about 489.675 grammes. According to the kilogramme definition, one livre was about 489.506 grammes. The difference is about 0.035%. However, a small difference in salinity (i.e. the difference between distilled water and very good quality drinking water) is enough to explain this difference.

The units in the following table are (except for the talent) calculated based on the kilogramme definition of the livre.

Table of mass units
Unit	Relative value	SI value	Imperial value	Notes
Poids de marc, mid-14th – late 18th century
prime	1/24^3 once	~2.213 mg
grain	1/24^2 once	~53.11 mg	~0.8197 grains	This is the French grain.
denier scruple [11]	1/24 once	~1.275 g	~19.67 grains
gros	1/8 once	~3.824 g	~2.158 dr
once	1/16	~30.59 g	~1.079 oz	This is the French ounce.
marc	1/2	~244.8 g	~8.633 oz
livre	1	~489.5 g	~1.079 lb	This is the French pound.
quintal	100	~48.95 kg	~107.9 lb	This is the French hundredweight.
talent
talent	~70.02	~34.28 kg	~75.57 lb	This is the mass of one French cubic foot of water; this value is calculated based on the French cubic foot and an assumed water density of 1 g/cm^3; other values in this table are based on the kilogramme definition.
bullion
felin	1/1280	~382.4 mg	~5.902 grains
maille	1/640	~764.9 mg	~11.8 grains
estelin	1/320	~1.53 g	~23.61 grains

See also

International System of Units Jean-Antoine Chaptal Mansus Mesures usuelles

Réaumur scale Systems of measurement Weights and measures

References

1. "History of measurement". Métrologie française. Retrieved 2011-02-06.
2. Adler, Ken (2002). The Measure of all Things—The Seven-Year-Odyssey that Transformed the World. London: Abacus. pp. 2–3. ISBN 0349115079.
3. See fr:Droit coutumier en France.
4. Russ Rowlett. "How Many? A Dictionary of Units of Measurement". Center for Mathematics and Science Education, University of North Carolina at Chapel Hill. Retrieved 2011-02-28.
5. Thierry Sabot (1 October 2000). "Les poids et mesures sous l'Ancien Régime" [The weights and measures of the Ancien Régime] (in French). histoire-genealogie. Retrieved 2011-02-10.
6. Denis Février. "Un historique du mètre" (in French). Ministère de l'Economie, des Finances et de l'Industrie. Retrieved 2011-03-10.
7. Yvette Darcy-Bertuletti (2005). "Tableau des mesures les plus courantes en usage dans le pays beaunois" [Table of the most widely used measurents in the Beaune locality] (PDF) (in French). Ville de Beaune. Retrieved 2011-02-25.
8. Suzanne Débarbat. "Fixation de la longueur définitive du mètre" [Establishing the definitive metre] (in French). Ministère de la culture et de la communication (French ministry of culture and communications). Retrieved 2011-03-01.
9. This can be shown by noting that 27706 x 16 = 443296 and that 9 x 16 = 144, the number of lignes in a pied.
10. Weights and Measures Act, Schedule III
11. Dictionnaire de l'Académie française. l'Académie francaise. 1694.