Units of measurement in France before the French Revolution
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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.
Contents
History
Although in the prerevolutionary era (before 1795) France used a system and units of measure that had many of the characteristics of contemporary English units (or the later Imperial System of units), France still lacked a unified, countrywide system of measurement. 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 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 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 preeminence 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 PerneslesFontaines in southeastern France differ from those cataloged 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
These definitions use the Paris definitions for the couture 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 had 6 pieds (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 nearidentical 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 prerevolutionary 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 9000/27,706 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 inch, 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 approximately 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 dm^{3} 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 kilogram was defined, the 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 grams. 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 kilogram definition of the livre.
Table of mass units  

Unit  Relative value 
SI value 
Imperial value 
Notes  
Poids de marc, mid14th – 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
References
 ^ ^{a} ^{b} "History of measurement". Métrologie française. Retrieved 20110206.
 ^ Adler, Ken (2002). The Measure of all Things—The SevenYearOdyssey that Transformed the World. London: Abacus. pp. 2–3. ISBN 0349115079.
 ^ See far: Droit couturier en France.
 ^ Russ Rowlett. "How Many? A Dictionary of Units of Measurement". Center for Mathematics and Science Education, University of North Carolina at Chapel Hill. Retrieved 20110228.
 ^ Thierry Sabot (1 October 2000). "Les poids et mesures sous l'Ancien Régime" [The weights and measures of the Ancien Régime] (in French). histoiregenealogie. Retrieved 20110210.
 ^ ^{a} ^{b} Denis Février. "Un historique du mètre" (in French). Ministère de l'Economie, des Finances et de l'Industrie. Retrieved 20110310.
 ^ Yvette DarcyBertuletti (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 20110225.
 ^ 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 20110301.
 ^ This can be shown by noting that 27706 x 16 = 443296 and that 9 x 16 = 144, the number of lignes in a pied.
 ^ Weights and Measures Act, Schedule III
 ^ Dictionnaire de l'Académie française. l'Académie francaise. 1694.
Further reading
 Cardarelli, François (2003). Encyclopaedia of Scientific Units, Weights and Measures: Their SI Equivalences and Origins. Springer Science & Business Media. pp. 79–83. ISBN 9781852336820.
 Palaiseau, JeanFrançoisGaspard (1816). Métrologie universelle, ancienne et moderne.