Originally, the Imperial system of Measurement was based on that used in the Roman Empire, and during that time, all were standardized. After the collapse of the Empire, the definitions of the measurements began to wander a bit until by the 18th C, they were completely different in different countrys and often different in separate regions of the same country.
Such was the situation in France at the time of the Revolution, and it was the need for a new standard that brought about the introduction of the Metric System. Eventually other countries adopted this new standard as well. It should be noted that in the century since its adoption, the length of the meter has been redefined a number of times until a standard that was based on a real figure could be rationalized (I believe it’s currently something like “the distance that light travels in 1.2 x 10^-9 seconds”).
I’ll define the major units first:
|Foot||The length of a man’s foot. A measure of length. From town to town, country to country, this measurement could differ, but as a rule a French Pied was equal to 12.8 English inches, while a Spanish Pie was 10.96 English inches|
|Gallon||An English measure of capacity. The imperial gallon contains 277.419 cubic inches: the wine gallon of 231 cubic inches is the standard in the United States.|
|Pound||A measure of weight and mass derived from the ancient Roman libra (which is equal to 327.25 grams), but this ancient standard has been modified variously over the course of time, and in different countries. The pound consisted originally of 12 ounces, corresponding more or less to that of troy weight. This is still used by goldsmiths and jewellers in stating the weight of gold, silver, and precious stones; but as early as the thirteenth or fourteenth century a pound of sixteen ounces was used for more bulky commodities. This was made a standard for general purposes of trade by Edward III, and known as the pound aveir de peis, i.e. of merchandise of weight, now called avoirdupois, q.v. At other times the pound has varied locally from 12 to 27 ounces, according to the commodity, pounds of different weight being often used in the same place for different articles, as bread, butter, cheese, meat, malt, hay, wool, etc.|
|Dram||A weight, orig. the ancient Greek drachma; hence, in Apothecaries’ weight, a weight of 60 grains =
1/8 of an ounce; in Avoirdupois weight, of 27.13 grains = 1/16 of an ounce; = drachm
|Ell||From the Latin “Ulna”. A unit of linear measure equal to 45 inches. The word ell seems to have been variously taken to represent the distance from the elbow or from the shoulder to the wrist or to the finger-tips, while in some cases a “double ell” has superseded the original measure, and has taken its name. English ell = 45 in. Scots = 37.2 in. Flemish = 27 in.|
|Furlong||Originally the distance an Ox could pull a plow before needing to rest, ie., “a furrow long”. As early as the 9th c. it was regarded as the equivalent of the Roman stadium, which was 18 of a Roman mile; and hence furlong has always been used as a name for the eighth part of an English mile, whether this coincided with the agricultural measure so called or not. The present statute furlong is 220 yards, and is equal both to the eighth part of a statute mile, and to the side of a square of 10 statute acres.|
|Grain||The weight of 1 Barleycorn (or one grain of Barley)|
|Hand||A unit of linear measure, formerly taken as equal to three inches, but now to four; a palm, a hand-breadth. Now used only in giving the height of horses and the like.|
|Inch||From the Latin “Uncia” (or a twelfth part), an inch is 1/12 Foot. A measure of length. In French, the unit of 1/12 a “foot” is the Pounce. In Spanish, Pulgadas. nb. A 12th of a Pounce is a Ligne, and a 12th of a Pulgadas is a Lignas. English inches are traditionally divided into 12 Lines. English inches are also defined as being the length of “Three good sized barleycorns
placed end to end”.
|League||An itinerary measure of distance, varying in different countries, but usually estimated roughly at about 3 miles; app. never in regular use in England, but often occurring in poetical or rhetorical statements of distance. Although the league appears never to have been an English measure, leuca occurs somewhat frequently in Anglo-Latin law-books (Bracton, Fleta, etc.); it is disputed whether in these works it means one mile or two.|
|Mark||A denomination of weight formerly employed (chiefly for gold and silver) throughout western Europe; its actual weight varied considerably, but it was usually regarded as equivalent to 8 ounces (= either 23 or 12 of a pound, according to the meaning given to the latter term).|
|Mile||Originally, the Roman lineal measure of 1,000 paces (mille passus or passuum), computed to have been about 1,618 yards. Hence, the unit of measure derived from this, used in the British Isles and in other English-speaking countries. Its length has varied considerably at different periods and in different localities, chiefly owing to the influence of the agricultural system of measures with which the mile has been brought into relation (see furlong). The legal mile in Britain and the U.S. is now 1,760 yards (5280 feet). The Irish mile of 2,240 yards is still in rustic use. The obsolete Scottish mile was longer than the English, and probably varied according to time and place; one of the values given for it is 1,976 yards.|
|Ounce||From the Latin “Uncia” (or a twelfth part), an ounce is 1/12 Pound (or was originally, and is still in “troy” weight). A measurement of weight.|
|Pace||A vague measure of distance with two widely differing definitions:
|Pint||A measure of capacity for liquids (also for corn and other dry substances of powdery or granular nature), equal to 1/2 a quart or 1/8 of a gallon; of varying content at different times and places.|
|Pound, Merchantile||(16 “Tower” oz.) is different from the Avoirdepois Pound (of 16 Avoirdepois oz), being a ratio of 36 Mercantile Pounds to 35 Avoirdepois Pounds|
|Pound, Tower||(12 “tower” oz.) used as a standard from Ethelred until Henry VIII abolished it in favor of the Troy Pound.|
|Quart||An English measure of capacity, one-fourth of a gallon, or two pints|
|Sack of Wool||Defined by Edward III to be equal to the weight of 26 times the Big Rock used to measure the “Aveir de peis” weight. That specific rock, or “Stone” weighed (at that time 14 pounds) (n.b., a sack of wool was equal in weight to 1/6th a cartload of lead) or 364 pounds aveir de peis.|
|Span||Generally the distance from the tip of the thumb to the tip of the little finger, or sometimes to the tip of the forefinger, when the hand is fully extended; the space equivalent to this taken as a measure of length, averaging nine inches.|
|Ton, or tun||A unit used in measuring the carrying capacity or burden of a ship, the amount of cargo, freight, etc.
|1 Grain (1/7000th Lb Avoirdupois)||=0.0648 grams|
|1 Pennyweight (i.e. the weight of one Anglo-Saxon/Carolingian penny)||= 1.3 grams|
|1 Penny Weight||= 1.55 grams|
|1 Dram (1/16 Oz Avoirdupois)||= 1.77 grams|
|1 Dram (1/8 of an ounce Troy)||= 3.89 grams|
|1 Shilling||= 18.67 grams|
|1 Ore (Anglo-Danish)||= 20.8 grams|
|1 Ore (Anglo-Saxon)||= 23.3 grams (or 24.88)|
|1 “Uncia”||= 27.2 grams|
|1 Ounce (Avoirdupois)||= 28.4 grams|
|1 Ounce (Tower)||= 29.2 grams|
|1 Once (French)||= 30.6 grams|
|1 Ounce (“Scotch Troy”)||= 30.8 grams|
|1 Ounce (Troy)||= 31.1 grams|
|1 “Tron” Ounce (Edinburgh/Scots)||= 38.97 grams|
|1 Mark (determined from the weight of the Anglo-Saxon penny)||=166.4 grams|
|1 Mark (Anglo-Saxon?)||= 226.8 grams|
|1 Mark (French)||= 245 grams|
|1 Pound (determined from the weight of the Anglo-Saxon penny)||=312 grams|
|1 Pound (Italian – low end)||= 300 grams|
|1 Roman Libre (12 Unciae)||= 326 grams|
|1 Pound (12 Tower Ounces)||= 349.9 grams|
|1 Pound (Italian – high end)||= 350 grams|
|1 “Livre de Charlemagne” (12 Onces)||= 367.5 grams|
|1 Pound (12 Troy Ounces)||= 373.25 grams|
|1 Pound (16 Avoirdupois Ounces)||= 453.6 grams|
|1 Pound (Hapsburg? low end)||= 459 grams|
|1 Pound (Mercantile; 16 Tower Oz.)||= 466.6 grams|
|1 Pound (Hapsburg? high end)||= 469 grams|
|1 Livre (French; 16 Onces)||= 490 grams|
|1 Pound (“Scotch”; 16 “Troy Oz”)||= 493.1 grams|
|1 Pound (“Dutch”; 16 Troy Ounces)||= 497.6 grams|
|1 Pfund (Modern)||= 500 grams|
|1 ? Pound (1/100 Hundredweight)||= 508 grams|
|1 Pint (East Anglia)||=567 grams|
|1 “Tron” Pound (Edinburgh/Scots)||= 623.5 grams|
|1 Mark (English)||= 746.6 grams|
|1 Clove (7 pounds Avoirdupois)||= 3175.2 grams (3.2 kg)|
|1 Nail or Clove (8 pounds Avoirdupois)||=3628.8 grams (3.6 kg)|
|1 Stone (12 Mercantile (listed in 1303))||= 5599.2 grams (5.6 kg)|
|1 Stone (14 pounds Avoirdupois)||= 6350.4 grams (6.4 kg)|
|1 “Quarter” weight||= 12700.4 grams (12.7 kg)|
|1 Fotmal (72 lbs Avoirdupois)||= 32659.2 grams (32.7 kg)|
|1 (“Quarter Sack”)||= 41277.6 grams (41.3 kg)|
|1 “Hundredweight”||= 50803.2 grams (50.8 kg)|
|1 Sack (???)||= 163296 grams (163 kg)|
|1 Sack (Wool)||= 165110 grams (165 kg)|
|1 Ton (2000 lbs Avoirdupois)||= 907200 grams (907 kg)|
|1 “Cartload of lead”||= 979776 grams (980 kg)|
|1 “Ton” (2240 lbs Avoirdupois)||= 1016064 grams (1016 kg)|
- Jones, Stacy V. Weights and Measures: An Informal Guide. Washington, D.C.: Public Affairs Press, 1963.
- Woolhouse, Wesley Stoker Barker. Historical, Measures, Weights, Calendars & Moneys of All Nations and an Analysis of the Christian, Hebrew and Muhammadan Calendars (with Tables up to 2000 A.D.). Chicago: Ares Publishers, 1979.
- Zupko, Ronald Edward. A Dictionary of English Weights and Measures: From Anglo-Saxon Times to the Nineteenth Century. Madison: University of Wisconsin Press, 1968.
- Zupko, Ronald Edward. French Weights and Measures before the Revolution a Dictionary of Provincial and Local Units. Bloomington: Indiana University Press, 1978.
- Zupko, Ronald Edward. Italian Weights and Measures from the Middle Ages to the Nineteenth Century Memoirs of the American Philosophical Society, 145. Philadelphia: American Philosophical Society, 1981.
- Zupko, Ronald Edward. A Dictionary of Weights and Measures for the British Isles the Middle Ages to the Twentieth Century Memoirs of the American Philosophical Society, 168. Philadelphia: American Philosophical Society, 1985.
- Zupko, Ronald Edward. Revolution in Measurement Western European Weights and Measures since the Age of Science Memoirs of the American Philosophical Society, 186. Philadelphia: American Philosophical Society, 1990.