A lot of the measurements found in historical documents are slowly disappearing from present knowledge so it
is useful to explain them here showing how they relate to current units. It is not particularly important but
where appropriate their approximate metric equivalent is given as an afternote in red.
Length - originally based on the human body
- Inch - the length of a thumb, Roman name ‘uncia’. At the time around 24.6mm long. (25.4mm)
- Hand - the width of a hand. Standardised at 4 inches. It is used to measure the height of horses up to the withers (shoulder). Three hands are a foot.
- Span - the length from your little finger to your thumb if you stretch your fingers. It later became 9 inches or a quarter of a yard.
- Foot - the length of a foot, Roman name ‘pes’. equal to 12 inches (304.8mm)
- Yard - the length from the fingertip of an outstretched arm to the tip of the nose. It was standardised at three feet or 36 inches. (910.4mm)
- Ell - originally twice the length of the arm from the elbow (‘elbow’ means the bend or bow of the ell or arm) to the tip of the middle finger,
later in England 45 inches or a yard and a quarter. It was mainly used for measuring widths of cloth. (1.143 m)
- Perch - the length of a measuring pole or staff, Roman name ‘pertica’ which was 10 pedes. It varied between 10 and 20 feet long but was standardised
in 1607 at 16½ feet or 5½ yards. It was also called a rod from the Old English rōd meaning a pole and was said to be the rod used by the
ploughman to encourage the oxen which was also useful to measure the land. The classic phrase used for the distance is a ‘rod, pole or perch’.
- Chain - this is a physical chain invented in 1620 used by land surveyor’s made up of 100 links and measuring 22 yards long.
- Furlong - short form of ‘furrow-long’ which was simply a convenient length for oxen to pull a plough before a brief rest while they turned round
on the headland to plough the next furrow. It was 40 rods or 220 yards long. Still used in describing the length of a horse race.
- Mile - the length of 1000 marching double paces based on the Roman army step, ‘mille passum’. It was around 4854 feet but the standard English
mile was later defined as 5280 feet or 1760 yards. (1.61km)
Area - widely used for land measurement
- Square perch - Also confusingly called a ‘perch’ the same as the length measurement. A square perch is an area equal to a square with each side
one perch long and equals to 30¼ square yards.
- Rood - or confusingly ‘rod’, this measurement was used in the Middle Ages, equal to 40 square perches
or a quarter of an acre.
- Acre - from the Old English ‘æcer’ meaning ‘open field’. The physical area of land
that a single oxen could plough in a day. A length of one furlong and a width of four rods, poles or perches. It was standardised
in 1878 at 4840 square yards so there are 640 acres in a square mile and 160 square perches in an acre. On tithe maps, land areas
were given in A.R.P., that is, acres, roods and perches. (0.4 hectares)
- Oxgang - or Bovate was the area of land that a single oxen could till in an annual ploughing season. Around 20 acres.
- Noke - a Middle English word from Latin ‘noca’. A quarter of a virgate or about 10 acres.
- Yardland - or Virgate was the area that a two-oxen plough could till in an annual ploughing season. Around 40 acres.
- Hide - from the Old English hi(gi)d, is related to the word hiwen, household, and is generally taken as
the area of mixed farmland which could support a household and was about 160 acres but it could be between 90 and 240 acres, possibly
depending on how fertile the land was. A hide equals four virgates or yardlands.
Weight - Avoirdupois and Troy systems
- Grain - in the Troy system, the average weight of a seed of corn. From the 12th century, it was used by
apothecaries when preparing medicines. Even today the sizes of some tablets are related to grains. A 300mg aspirin
tablet is roughly equivalent to a 5 grain tablet. (64.799 milligrams)
- Pennyweight - 24 grains. Its abbreviation is dwt.
- Ounce - Troy, possibly named after the French market town of Troyes - 480 grains or 20 pennyweights.
Used by jewellers for weighing gold, silver and precious stones. (31.103 grams)
- Ounce - Avoirdupois, from Norman-French meaning ‘goods measured by weight’ - 437 grains,
after 1558 half a grain more. Used in general commercial trade and it’s abbreviation is oz. (28.349 grams)
- Pound - originally based on the Roman pound or ‘libra’, and the abbreviation for pound was always lb.
Three systems have been used in England - Tower, Troy and Avoirdupois.
- Pound - Troy, equals 12 troy ounces. It was equivalent to 240 pennyweights or 5760 grains.
- Pound - Tower, equals 12 tower ounces or 7,680 tower grains. The name refers to a standard kept at the Tower of
London. In this system, the tower grain was about 0.7 times the weight of the troy grain. Henry VIII ended the use of tower
weights in 1526.
- Pound - Avoirdupois, equals 16 avoirdupois ounces. It appeared in the 14th century as the ‘wool pound’
In 1588 Queen Elizabeth increased its weight from 6992 grains to 7000 grains. It is still used in the USA.
(exactly 453.59237 grams)
- Stone - 14 pounds; but in Herefordshire sometimes 12 pounds particularly in weighing wool or yarn.
- Hundredweight - 112 lbs., 8 stone or one-twentieth of a ton. In the USA 100 lbs. The abbreviation for hundredweight
- Ton - 20 cwt. or 2240 lbs. In the USA 2000 lbs. From the vat or vessel called a ‘tun’ from Old English ‘tunne’
which could weigh up to 2000 lbs. (1016/907 kilograms)
Volume - storing ale, beer, wine and similar
- Pint - an eighth of a gallon (568 millilitres)
- Gallon - from Norman-French ‘galun’. It was a measure of wine and ale, the wine gallon being 231 cubic inches and the larger ale gallon 282
cubic inches. In 1824, these were combined into the imperial gallon of 277.4194 cubic inches. (4.546 litres)
- Pin - 4½ gallons or 36 pints. In use today. (568 millilitres)
- Firkin - two pins, nine gallons or a quarter of a barrel. The ale firkin grew from 8 ale gallons to 8½ in 1688 to 9 in 1803 and was standardised as 9
imperial gallons in 1824. Still in use today.(41 litres)
- Kilderkin - two firkins or half a barrel. It’s volume changed in line with the firkin, finally settling at 18 gallons.
- Barrel - from 1688 this was 34 ale or beer gallons or 31½ wine gallons; after 1803, 36 ale or beer gallons, and after 1824,
both ale and wine barrels were made equal to 36 standard gallons. There are six barrels in a tun. (164 litres)
- Hogshead - from 1688 this was 51 ale or beer gallons or 63 wine gallons and equal to 1½ barrels of ale or 2 barrels of wine;
after 1803, it became 54 ale or beer gallons, and after 1824, both ale and wine hogsheads were made equal to 54 standard gallons.
A hogshead is half a butt or quarter of a tun. (245 litres)
- Puncheon - one-third of a tun (327 litres)
- Butt - or Pipe. Half a tun, equal to 3 barrels. (491 litres)
- Tun - from Old English ‘tunne’ meaning vat or vessel with a volume of 6 barrels. It held held 204 ale gallons or 252 wine gallons.
In 1803 the tun of ale was increased to 216 gallons and the two barrels were standardised to the English imperial tun of 216 gallons after 1824. (982 litres)
Volume - measuring dry goods such as grain
- Peck - a standard container size holding a volume of 2 gallons and weighing about 14lbs. (9.1 litres)
- Bushel - from the Old French word ‘boissiel’ meaning box this a standard container holding a volume of 8 gallons
and weighing about 56lbs. About 2200 cubic inches. (36.4 litres)
- Chaldron - a standard container holding a volume of 36 bushels and used particularly for coal.
Note: all gold and silver coins produced since 1981 by the Royal Mint are not definitives (coins for circulation) but commemoratives (coins for collectors) and bullion (sold for their weight of precious metal).
- Denarius - a Roman silver coin, which led to the French silver ‘denier’ which gave its abbreviation d. to pennies ever since.
- Penny - the silver penny replaced the Anglo-Saxon ‘sceatta’ and was in use from the time of Eadgar up to 1816 when
copper pennies were introduced.
- Farthing - this coin was around from 1619 to 1960, first in silver, lastly in copper. It was a quarter of a penny.
- Groat - worth four pennies, this silver coin was introduced by King Edward in 1279.
- Shilling - Charlemagne divided the silver pound into 20 solidi or sous. The silver (later cupro-nickel) shilling was
in circulation from 1505 to 1971 and equalled 12 pence.
- Florin - the name comes from two Florentine engravers who produced an unsuccessful gold florin in 1344 valued at
6 shillings. What was in effect
the first decimal coin, the silver florin, was introduced in 1849, worth 2s. or one tenth of a pound.
- Crown - Henry VIII introduced the gold crown, valued at 5 shillings, in 1526. Edward VII issued it as a silver coin
- Noble - a gold coin introduced by Edward III in 1345, it was worth half a mark or 6s.8d. (80 pence)
- Angel - introduced by Edward IV in 1464 when the noble was revalued at 8s. 4d. (120 pence) and the new gold angel
became 6s.8d. It was minted up to 1643.
- Mark - a monetary weight unit in the 9th century. It was the weight of 100 pennies @ 22½ grains = 2,250 grains.
It became a unit of money and was valued at ⅔ of a pound in the time of Charlemagne, equal to 160 pence or 13s.4d. In England
it was never issued as a coin but was used in accounting for rents, taxes etc.
- Sovereign - a gold coin that appeared in 1817 when coinage moved from the silver standard to the gold standard. It
was made of 8 grammes of 22 carat gold and in 1526 it’s value was 22s. Mainly used as bullion (see note below).
- Pound - the monetary pound was a banknote since but was replaced by a coin in 1983.
The abbreviation symbol ‘£’ harks back to the first two letters of the Roman word for the pound weight ‘libra’.
- Guinea - started off in as 20s. but, under George I in 1717, the guinea was revalued to 21s. Used in horse racing prizes.