In England, before 13th – 19th centuries, an important unit of mass used for wool, = 350 pounds before approx. 1256 and 364 pounds thereafter. link to a chart showing relationships between units of mass in 13th century England

The original magnitude of the sack may have been influenced by the monetary value of the wool. A law of the tenth century (III Edgar 8.2) states “And a wey of wool shall be sold for 120d.  And no one shall sell it at a cheaper rate.”¹ A wey of wool is half a sack, so a sack would have been sold for 240 pence, or exactly a monetary pound.

Thirteenth-century documents define the sack as 28 stone each of 12½ pounds avoirdupois, or 350 pounds, but its value was already shifting.

Wholesale quantities of wool were weighed on the King's balance, and it was the custom to add extra wool until the balance tipped in the buyer's favor. Such a procedure is easily abused by a weighmaster who wishes to favor the buyer, since the scales can be as easily tipped by an extra ten pounds as an extra two. So London abolished this practice effective December 6, 1256. To compensate buyers for the change to exact weight, they were given two well-defined extra bits: “tret,” an extra 4 pounds for every 100 pounds purchased,² and “cloffe”, an extra 2 pounds for every 300 pounds purchased. A 350-pound purchase (the old sack) thus became 350 plus 14 (14 = 4 × 3, plus 2), or 364 pounds. That weight was coincidentally almost the same as 500 libbrae of the city of Florence, one of England's most important customers in the wool trade.

The 364-pound sack was legalized by Edward III in 1340,3 when he declared the sack weighed 26 stones, each stone weighing 14 pounds. These values for the stone and sack survived for six centuries. But see stone.

In Tudor times, for customs purposes 240 woolfells were considered equal to 1 sack.

For a full discussion of this subject, see:

1. Agnes Jane Robertson.
The Laws of the Kings of England from Edmund to Henry I.
Cambridge: Cambridge University Press, 1925.

Page 29.

2. R. D. Connor.
The Weights and Measures of England.
London: Her Majesty’s Stationery Office, 1987.

Connor, however, doesn't quite distinguish between tret and cloffe.

3. Statute 14 Edward III Stat i c 21 (1340).



Mekly besecheth your humble suppliant R. A. citesen and habur' of the cite of London and whereon Jhn Derby citezen and drap and late Aldirman of the said cite the xxiij. day of Junij now late past bargeyned with your said suppliant and sold unto him xij. bales of peper then beyng within the mansion place off the said John set in the perish of Seint Denys Bakchirch of London which xij. bales than and there weied grose be his weights iij. M. C. xxvi.ll. sotel iij. M. iiij. C. xxxxviij.ll. wherof by couenaunt made betwixt the said J. D. and your said suppliat shulde be rebated for the tare of euery of the said xij. bales iiij. li. and for the cloff of euery off the said xij. bales ij. ll. som lxxij. ll. and for the tret of the same peper C. xxxvij. ll. and also rest iij. M. ij. C. xxxxix. li. p'ce of euery pounde of the same rest xv. d'. som in money xi. s. iij.d'. too be paid at iij. payments

Meekly beseecheth your humble supplicant R. A., citizen and resident of the city of London, and on whom John Derby, citizen, draper and former alderman of the said city, the 23 day of June now late past bargained with your said supplicant and sold unto him 12 bales of pepper then being within the dwelling house of the said John, in the parish of St. Denys Bakchurch of London, which 12 bales then and there weighed

gross by his weights 3126 pounds

sottil 3448 pounds

whereof by covenant made betwixt the said J.D. and your said supplicant should be rebated 

for the tare of every of the said 12 bales 4 pounds, [so 48 pounds] and 

for the cloff of every of the said 12 bales, 2 pounds, [so 24 pounds. 24+48=72] sum 72 pounds, and

for the tret of the same pepper 137 pounds and also [should be 167]  [104+ 37 = 

remaining 3249 pounds [3448 − 72 − 167 = 3209] 

price of every pound of the same remaining 15 pence

[3209 × 15 pence = 48135 pence; which = ]

sum in money 200 pounds 11 shillings 3 pence, to be paid in 3 payments. [at 15d/lb , for 3209 pounds]

Richard Arnold.
In this Booke is conteyned the Names of the Baylifs, Custos, Mairs, and Sherefs,of the Cite of London, from the Tyme of King Richard the Furst; and also th'Artycles of the Chartur and Libarties of the same Cyte ; and of th'Chartur and Liberties off England, wyth odur dyvers mat's good and necessary for every Citezen to undirstond and knowe.
[Antwerp: John Doesborowe?, 1503?.]
Reprinted as
The Customs of London, otherwise called Arnold's Chronicle; containing among divers other matters, …
London: Printed for F. C. and J. Rivington; T. Payne; Wilkie and Robinson, Longman, Hurst, Rees, Orme and Brown; etc., 1811.
Pages 127-128 (of the 1811 edition).


[In the year 1256, Henry III accused the London merchants of cheating:]
Then was layde to their charge, that besyde many wronges by them done to the king, and to the communaltie of the Citie : they had altered the kinges Beame, and ordered it to the advauntage of themselves, and of the riche men of the Citie. Whereunto the parties aunswered and said, that the alteration of the Beame was not done by them onely, but by the advice and consent of five hundreth of the best of the Citie. For where before the Weyer used to leane his draught toward the Marchandice, so that the buyer had by that meane. x. or. xij. pound in a draught to his advauntage, and the seller so much disadvauntage, nowe for indifferencye and equalitie of both persons or Marchauntes, was ordeyned that the Beame should stande upright in the cleft thereof, enclinyng to neyther partie, as it doth in weiyng of Golde and Silver, and the buyer to have of the seller allowed unto him for all thinges* foure pounde of the hundreth.

*This is that allowance that Grocers call Cloffe. [marginal note in 1809 edition]

Richard Grafton.
A Chronicle at Large and meer history of the affayres of England and Kinges of the Same, …
[London : Imprinted by Henry Denham, dwelling in Paternoster Rowe, for Richarde Tottle and Humffrey Toye], 1569.
From the edition
Grafton's Chronicle; or History of England, … From the year 1189 to 1558; Inclusive.
London: Printed for J. Johnson; F. C. and J. Rivington; T. Payne; Wilkie and Robinson; Longman, Hurst, Rees and Orme; Cadell and Davies; and J. Mawman, 1809.
Volume 1, page 258.


And because in England all wares of Volume or Bulck is sold, some by the hundreth weight of 112 [pound symbol], and some is sold by the pound, as spices, sugars, and such like, & yet are weighed by the said weight of 112 [pound symbol]; and that moreover there is an over-weight allowed called Trett which is 4 upon the 112 [pound symbol], and also 2 [pound symbol] upon every skale of 3 hundreth weight called Cloff, which is abated betweene the buyer and seller, and so there is a losse of weight by this Trett and Cloff.

Gerard Malynes.
Vel Lex Mercatoria, or the Ancient Law-Merchant.…
London: Printed by Adam Islip, 1622.
Page 22.


The Sacke of Wooll appointed by King Edward the third, is distinguished according to the Lunare yeare of 13 moneths, of 28 dayes, making in all 364 [symbol pound], or 365 [symbol pound], for so many dayes in the yeare ; the Todd of Wooll being 28 [pound symbol], for so many dayes in the moneth ; and 13 Todds for so many moneths in the yeare; every Todd containing foure Nayles, and every Nayle being seven [pound symbol], for the seven days of the weeke.

Gerard Malynes.
Vel Lex Mercatoria, or the Ancient Law-Merchant.…
London: Printed by Adam Islip, 1622.
Page 56.

A good example of a folk derivation of the magnitude of a unit, apparently recorded in Jeake's Arithmetick (1696) and repeated as late as the 19th century:

It is to be observed here that a sack is 13 tods, and a tod 28 pounds, so that the sack is 364 pounds. Jeake says this was arranged (31 Edward III, cap. 8) according to the lunar year of 13 months of 28 days each. The reason no doubt was that the multitudes of whose occupation the spinning of wool formed a part might be able to instantly calculate the supply for the year or month from the amount of the day's work; a pound a day being a tod a month and a sack a year.

The Penny Cyclopaedia of the Society for the Diffusion of Useful Knowledge. Vol. XXVII. Wales-Zygophyllacaeae.
London: Charles Knight and Co., 1843.
Page 202.

It is doubtful that a 14th-century English cottager had a way of weighing the day's output. In any case, the statutes of that day generally served the convenience of merchants more than that of the “multitudes.”


In Scotland, a unit of mass used for wool, 24 stone of 16 pound each.

Worlidge (1702).


In England, a unit of mass used for cotton, = 150 to 400 pounds.


In England, a unit of capacity used for coal, described in 1552 as equaling 4 bushels. An act of Parliament in 1730 defined the capacity of the sack as 3 bushels (the bushel had shrunk since 1552), and fixed the dimensions of the physical object: 50 inches long and at least 20 inches broad. Twenty-eight years later Parliament lengthened the sack by 2 inches. In the Act of 1824 that established imperial measure, the sack was set at 3 heaped imperial bushels, about 136.3 liters.



The Act of the 3rd of George the 2nd, A. D. 1730, Chap. 26, Sect. 11, enacts (for preserving and discovering Frauds and Abuses in the measuring of Coals) that all Coals, landed at any Wharf, or other landing place on the River Thames, and which shall be carried to any Places within the Cities or Suburbs of London and Westminster, shall be carried in linen Sacks, sealed and marked, which Sacks shall be full four Feet and two Inches in Length, and twenty-six inches in Breadth after they shall be made; and all Dealers in Coals shall use no other; and Makers of Coal Sacks shall make them of the Dimensions aforesaid at least.

Great Britain. Parliament. House of Commons.
Reports from committees of the House of Commons which have been printed by order of the House, and are not inserted in the Journals. Volume II.

[Lord Carysfort's Commission.]
Report from the committee appointed to inquire into the original standards of the weights and measures in this kingdom, and to consider the laws relating thereto. 26 May 1758
Page 418.


In the Netherlands, a unit of capacity: Amsterdam, 79.530 liters; in Vlissingen, 86.349 liters.


In the United States, a series of sizes of flour sacks based originally on the English 14-pound stone. One flour sack size was 10 stones, that is, 140 pounds. The flour barrel, of 14 14-pound stones, or 196 pounds, was subdivided into a series of sacks containing 98, 49, 24½ or 12¼ pounds of flour. These sizes were sometimes defined by state laws. But states also set slighty different standards, such as 24 pounds or 25 pounds for the eighth-barrel sack.



[The 140-lb sack of flour]

At present a popular package in use by nearly all large bakers and a great number of smaller bakers is a 140-pound sack, the old English 10-stone package. It has been a handy package for both the miller and the baker in that it requires no special calculation, as it breaks seven packages to 140 pounds of flour, being equivalent to 5 bushels. The package is popular because 100 pounds is not a full man's load, either to carry or truck, but 140 pounds is such a package as a man can handle comfortably, and the package itself, the empty package, has had a resale value to a degree which the 100-pound and 98-pound cotton sack has not had. The jute sack—the 140-pound sack is a jute sack—has had a resale value of sufficient amount as to make it a very desirable package for the baker, because he can frequently sell his 140-pound empty jute sack for 6 or 7 cents apiece, the net result being that it reduces the cost of his flour about 10 cents a barrel. If he is careful with his sacks, the sacks can be used over again. I have heard millers say it was a better sack to bag flour in a second time, because the interstices of the weave were filled in and there was less filtration of flour through it. The 140-pound sack will be continued as an export package. There is no question about that, because the English base their business upon a 280-pound bag, with a 140-pound sack known to them as half a bag.

U.S. House of Representatives. Committee on Coinage, Weights and Measures.
To establish standard measures for flour, meal, and feed.
Sixty-Fifth Congress, Second Session on H.R. 10957. April 16, 1918.
Washington: G. P. O., 1918.
Pages 9 -10. Testimony of A. P. Husband, secretary of the Millers' National Federation.


[Flour sacks whose capacities were subdivisions of the flour barrel]

Please see one of the sources for the flour barrel.


Mr. Brokeby informs me, that with them in the East Riding of Yorkshire, the Word Sack is appropriated to a Poke that holds four Bushels, and that Poke is a general Word for all Measures.

John Ray.
A Compleat Collection of English Proverbs … 4th Edition.
London: Printed for W. Otridge, etc. 1768.
Page 49. This volume incorporates Ray's Collection of English Words, first published in 1674, and in an enlarged edition in 1691.

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