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The traditional French units of measurement prior to metrication were established under Charlemagne during the Carolingian Renaissance. Based on contemporary Byzantine and ancient Roman measures, the system established some consistency across his empire but, after his death, the empire fragmented and subsequent rulers and various localities introduced their own variants. Some of Charlemagne's units, such as the king's foot (French: pied du Roi) remained virtually unchanged for about a thousand years, while others important to commerce—such as the French ell (aune) used for cloth and the French pound (livre) used for amounts—varied dramatically from locality to locality. By the 18th century, the number of units of measure had grown to the extent that it was almost impossible to keep track of them and one of the major legacies of the French Revolution was the dramatic rationalization of measures as the new metric system. 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.
History
Although in the pre-revolutionary 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 had 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. Some of the differences were large: for example 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]
Tables of units of measure
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 medieval 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 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 around 11 mm (0.55%) shorter.
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.[5]
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 or rood), the arpent and the lieue (league) had a number of variations, particularly the aune (which was used to measure cloth).[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".[7] Thus the French royal foot is exactly 9000/27 706 metres (about 0.3248 m).[8]
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.[9] This makes the Quebec pied very slightly smaller (about 4 parts in one million) than the pied used in France.
| Unit | Relative value (pieds) |
SI value (approx.) |
Imperial value (approx.) |
Notes | |
|---|---|---|---|---|---|
| point | 1⁄1728 | 0.188 mm | 7.401 thou | 1⁄12 of a ligne. This unit is usually called the Truchet point in English. Prior to the French Revolution the Fournier point was also in use. It was 1⁄6 of a ligne or 1⁄864 of the smaller French foot. | |
| ligne | 1⁄144 | 2.256 mm | 88.81 thou | 1⁄12 of a pouce. This corresponds to the line, a traditional English unit. | |
| pouce | 1⁄12 | 27.07 mm | 1.066 in | 1⁄12 of a pied du roi. 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 |
Six pieds du roi. This corresponds to the fathom, a traditional English unit. Unlike the fathom, it was used in both land and sea contexts. The Toise du Chatelet was introduced in 1668 and defined by an iron bar on the Grand Chatelet. This was replaced by the Toise du Perou in 1766.[10] | |
| Paris | |||||
| perche d'arpent | 22 | 7.146 m | 7.815 yd | Related to, but not directly corresponding with, the English perch or rod (which is 16+1⁄2 feet, approximately three-quarters of the French perche). | |
| arpent | 220 | 71.46 m | 78.15 yd | Ten perches. | |
| lieue ancienne | 10 000 | 3.248 km | 2.018 miles | This is an old French league, defined as 10 000 (a myriad) pieds. 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 '. After 1737, it was also called the "league of bridges and roads" (lieue des Ponts et des Chaussées). | |
| lieue des Postes | 13 200 | 4.288 km | 2.664 miles | This league is 2200 toises or 60 arpents. 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. (Compare the international nautical mile, of which 60 make one degree; one lieue therefore equaling 2.4 nautical miles.) 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 (du roi) | 180 | 58.47 m | 63.94 yd | Ten perches du roi. | |
| Local | |||||
| perche ordinaire | 20 | 6.497 m | 7.105 yd | This perch was used locally. | |
| arpent (ordinaire) | 200 | 64.97 m | 71.05 yd | Ten perches ordinaires. | |
- The French typographic point, the Didot point, was 1⁄72 of a French inch, i.e. two royal points. The French pica, called Cicéro, measured 12 Didot points or 1⁄6 inch.
Area
| Unit | Relative value (pieds carrés) |
SI value |
Imperial value |
Notes | |
|---|---|---|---|---|---|
| pied carré | 1 | ~1055 cm2 | ~1.136 sq ft | The French square foot | |
| toise carrée | 36 | ~3.799 m2 | ~40.889 sq ft, or ~4.543 sq yd |
The French square fathom | |
| Paris | |||||
| perche d'arpent carrée | 484 | ~51.07 m2 | ~61.08 sq yd | This was the main square perch in old French surveying. It is a square 22 pieds du roi on each side. | |
| vergée | 12 100 | ~1277 m2 | ~1527 sq yd | A square 5 perches on each side, or one quarter of an acre. | |
| acre, or arpent carré |
48 400 | ~5107 m2 | ~6108 sq yd, or ~1.262 acres |
The French acre is a square 10 perches (one arpent) on each side. (Does not exactly correspond to the English acre, which is defined as 43 560 square feet.) | |
| North America | |||||
| perche du roi carrée | 324 | ~34.19 m2 | ~40.89 sq yd | This square perch was used in Quebec and Louisiana. It is a square 18 pieds du roi on each side. | |
| vergée (du roi) | 8100 | ~854.7 m2 | ~1022 sq yd | A square 5 perches du roi on each side. | |
| acre (du roi), or arpent carré |
32 400 | ~3419 m2 | ~4089 sq yd, or ~0.8448 acres |
A square 10 perches du roi 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 m2 | ~50.48 sq yd | This square perch was used locally. It is a square 20 pieds du roi on each side. | |
| vergée (ordinaire) | 10 000 | ~1055 m2 | ~1262 sq yd | A square 5 perches ordinaires on each side. | |
| acre (ordinaire), or arpent carré |
40 000 | ~4221 m2 | ~5048 sq yd, or ~1.043 acres |
A square 10 perches ordinaires on each side. | |
Volume – liquid measures
| Unit | Relative value (pintes) |
SI value |
U.S. value |
Imperial value |
Notes |
|---|---|---|---|---|---|
| roquille | 1⁄32 | ~29.75 ml | One quarter of a poisson. | ||
| poisson | 1⁄8 | ~119 ml | A measure equal to a half a demiard. There were different sizes based on the commodity measured: poisson de vin (wine), poisson de eau de vie (brandy), or poisson de lait (milk).[11] | ||
| demiard | 1⁄4 | ~238 ml | ~0.5 pint | demi in French means "half": in this case, half a chopine, and – coincidentally – 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 pied du roi. |
| quade | 2 | ~1.904 L | ~0.5 gallon | ~0.42 gallon | |
| velte | 8 | ~7.617 L | ~2.01 gallon | ~1.68 gallon | a velte was a measuring stick that was inserted into a cask or barrel to determine its depth. |
| quartaut | 72 | ~68.55 L | 9 veltes, or two cubic pieds du roi. | ||
| feuillette | 144 | ~137.1 L | |||
| muid | 288 | ~274.2 L | Eight cubic pieds du roi. | ||
| cubic | |||||
| pouce cube | 1⁄48 | ~19.84 ml | The French cubic inch. | ||
| pied cube | 36 | ~34.28 L | The French cubic foot. In ancient times, a cubic foot was also known as an amphora when measuring liquid volume. | ||
Volume – dry measures
| Unit | Relative value (boisseaux) |
SI value |
Imperial value |
U.S. value |
Notes |
|---|---|---|---|---|---|
| litron | 1⁄16 | 793.5 cm3 | 0.1745 imp gal | 0.1801 U.S. dry gal | 1⁄4 of a quart. The litre is etymologically related to this unit. |
| quart | 1⁄4 | 3.174 dm3 | 0.698 imp gal | 0.721 U.S. dry gal | 1⁄4 of a boisseau. |
| boisseau | 1 | 12.7 dm3 | 2.8 imp gal | 2.9 U.S. dry gal | Although etymologically related to the English unit bushel, the French bushel is about one third the size. A boisseau was defined as 10⁄27 of a cubic pied du roi. |
| minot | 3 | 38.09 dm3 | 8.38 imp gal | 8.65 U.S. dry gal | |
| mine | 6 | 76.17 dm3 | 16.76 imp gal | 17.29 U.S. dry gal | |
| setier | 12 | 152.3 dm3 | 33.5 imp gal | 34.6 U.S. dry gal | |
| muid | 144 | 1.828 m3 | 402 imp gal | 415 U.S. dry gal | |
| cubic | |||||
| pouce cube | 1⁄640 | ~19.84 cm3 | ~1.211 cu in | The French cubic inch. | |
| pied cube | 2+7⁄10 | ~34.28 dm3 | ~2,092 cu in | The French cubic foot. Exactly 2.7 boisseaux. | |
Mass
| Abbeville | 93–94 |
| Avignon | 83 |
| Beaucare | 95 |
| Bordeaux | 100 |
| Bourg-en-Bresse | 96 |
| Dunkirk | 87 |
| Lille | 87–88 |
| Lyon | 87 |
| Marseilles | 81 |
| Montepellier | 83 |
| Nancy | 94–95 |
| Nantes | 101–102 |
| La Rochelle | 101–102 |
| Rouen (poids de vicomté) | 103 |
| Strasbourg (petit poids) | 96 |
| Toulouse | 84 |
| Nominal (marcs) |
Error in actual (grains) |
|---|---|
| 20 | +1.4 |
| 14 | +4.5 |
