The Measurement Archive
A compendium of historical measures and modern converters. Explore the fascinating history of measurement units used throughout British history.
All Units
Browse the complete compendium of measurements and tools.
Acre (ac)
Historically the amount of land a team of eight oxen could plough in one day. Approx. 4,840 square yards. Still used in the UK for land measurement.
4,046.86 square metres
Acre-Foot
One foot of water spread over one acre, being twelve acre-inches, and the standard unit of reservoir capacity and water allocation.
43,560 cubic feet = 1,233,482 litres = 271,328 imperial gallons
Acre-Inch
One inch of water spread over one acre, being the working volume of irrigation and land drainage.
3,630 cubic feet = 102,790 litres = 22,611 imperial gallons
American Standard Barrel
The absolute workhorse barrel of the global whisky industry, heavily charred to release sweet sugars.
200 Litres (Cask)
Ampere (A)
Named after André-Marie Ampère, measuring the volume of electrons flowing past a point per second.
1 Coulomb per second
Angel
An official 1465 gold coin depicting the Archangel Michael slaying a dragon, replacing the Noble.
Originally 6s 8d (80 pence), later 10s ≈ £0.50 (face value)
Angels' Share
The volume of spirit lost to evaporation through the oak during maturation, reckoned at roughly two per cent a year in Scotland.
Approx. 2% per annum in Scotland; considerably more in warmer climates
Anker
A small Dutch cask of about 38 litres, sized so that a single person could carry it, and the standard vessel of the Georgian contraband trade.
10 wine gallons = 37.85 litres (8.3 imperial gallons)
Apothecaries’ Ounce (℥)
The dispensing ounce of the pharmacopoeia, identical in weight to the troy ounce but subdivided entirely differently.
480 grains = 31.1035 grams
Apothecaries’ Pound
The nominal top of the apothecaries’ scale, at twelve ounces or 5,760 grains, and identical in weight to the troy pound.
5,760 grains = 373.24 grams
Atmosphere (atm)
A standard pressure unit defined relative to average air pressure at sea level.
101,325 Pascals
Baker's Dozen
The classic British protective buffer (12+1) used by medieval tradesmen to guarantee compliance with royal market laws.
13 units
Bale (Paper)
A major wholesale storage and transport unit comprising 5 bundles or 10 reams.
5,000 sheets
Bar
A non-SI metric unit widely used in high-pressure systems, roughly equivalent to atmospheric pressure.
100,000 Pascals
Barleycorn
Standardised in 1324 by King Edward II as the length of three dry grains of barley laid end to end.
1/3 inch = 8.47 millimetres
Barrel
The reference cask of the British brewing trade, holding 36 imperial gallons and anchoring the entire cask hierarchy.
36 imperial gallons = 163.66 litres
Bind
A historic fish trade unit grouping 250 fish (like eels) into uniform batches for transport and regional rent payments.
Approx. 250 fish
Blood-Tub
The smallest traditional cask in the cooperage, historically favoured for small experimental whisky ageing batches.
35 Litres (Cask)
Boll
The principal Scots dry measure for grain, holding four firlots, and the unit in which rents and stipends were commonly paid.
Approx. 145 litres for wheat; larger for oats and barley
Bolt
A traditional commercial standard representing a full, finished roll of woven fabric or canvas, traditionally measuring exactly 40 yards of textile material.
40 yards = 36.58 metres
Bore (Gauge)
The diameter of a gun barrel, expressed as the number of spherical lead balls of that diameter which together weigh one pound.
12-bore = 18.5 mm; 20-bore = 15.6 mm
Brace
A traditional counting term denoting a pair of items or animals, derived from what can be held in both arms.
2 units
British Thermal Unit (Btu)
The quantity of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
1,055.06 joules
Bushel (bu)
A traditional dry volume measure equal to 8 gallons used for agricultural goods.
36.37 litres
Byte (B)
Coined by Werner Buchholz in 1956 and deliberately misspelled to prevent accidental mutation to "bit".
8 bits
Cable Length
One tenth of a nautical mile, and originally the working length of a ship’s anchor cable.
185.2 metres = 607.6 feet
Calorie (cal)
The heat required to raise one gram of water by one degree Celsius, introduced by French chemists in the early nineteenth century.
4.1868 joules
Candlemas
A traditional Scottish legal term day and calendar quarter day falling on February 2nd.
February 2nd
Carat / Fineness
A metric used by the Royal Mint and goldsmiths to measure the purity of precious metals.
925 parts per thousand (sterling silver standard)
Carucate
The Danelaw equivalent of the hide, defined as the land a plough team of eight oxen could work through a full year.
Approx. 120 acres = 485,623 square metres
Cast (Fish)
A handful of fish cast aside as make-weight, allowing buyers a margin for undersized or broken fish without the need for inspection.
Pilchards: 5 fish. Mackerel at Newlyn: 12 fish, being 3 warps
Celsius (°C)
The metric temperature scale officially adopted across the UK during metrication in the 1970s.
Water freezes at 0°C and boils at 100°C
Centilitre (cl)
One hundredth of a litre, and the customary labelling unit for European wine and spirit bottles.
10 millilitres = 0.01 litres
Chain (ch)
Introduced by Edmund Gunter in the 17th century using a physical surveying chain. A cricket pitch is one chain long.
22 yards = 20.1168 metres
Chapman’s Dozen
A 13-unit trade bonus or wholesale allowance used by travelling peddlers and hawkers.
13 units
Christmas
One of the four traditional Quarter Days in the British legal and calendar year.
December 25th
Clove
An old English weight unit used for wool and cheese, representing half a stone.
7 pounds = 3.175 kilograms
Cord
One hundred and twenty-eight cubic feet of stacked firewood, being a pile four feet high, four feet deep and eight feet long.
128 cubic feet = 3.62 cubic metres
Corf
An underground mining container used in British collieries to haul newly hewn coal from the tunnel face to the surface.
4 to 7 hundredweight
Coulomb (C)
The SI unit of electric charge, defined as the quantity carried by a current of one ampere flowing for one second.
1 ampere-second
Cowel
A rectangular trough-shaped basket with squared ends and a plaited head-band, carrying three hundreds of pilchards on the carrier’s back.
3 hundreds = approx. 360 pilchards, 50–55 lb
Cran
A legal volume unit used along Scottish and East Anglian coasts for freshly landed herring, holding about 1,200 fish.
170.48 litres
Crown
A large, prestigious historical British silver coin worth five shillings.
5 shillings = £0.25 (modern)
Crumb
A minor digital storage unit consisting of two bits, representing a quarter of an 8-bit byte.
2 bits
Cubic Inch (cu in)
The volume of a cube one inch on each side, and the dimension in which English liquid measures were legally defined.
16.387 millilitres
Cubit
An ancient historical length unit based on the physical length of a forearm.
18 inches = 0.4572 metres
Deal
A sawn softwood plank of customary size, typically nine inches wide by three thick, and the basic trading piece of the Baltic import trade.
Typically 9 × 3 inches in section, in lengths from 8 to 21 feet
Decibel (dB)
A logarithmic scale mapping sound intensity to mimic the human ear’s non-linear perception.
Logarithmic sound ratio unit
Devil's Cut
The spirit absorbed into the oak staves and left behind when a cask is emptied, amounting to several litres a barrel.
Roughly 2–3 gallons per barrel, varying with wood and age
Dicker
A historical English commercial tally of exactly ten items, widely used for hides, skins, and gloves.
10 units
Double-Decker Buses
A classic, quirky British media benchmark answering the common question of how heavy a standard London bus is.
12,000 kilograms (12 Tonnes)
Dozen (doz)
A staple grouping unit of 12 derived from the duodecimal counting system.
12 units
Drachm (Apothecary)
An ancient apothecary mass unit equivalent to 60 grains used by chemists to weigh precise ingredients.
3.89 grams
Dram
A traditional measure of spirits celebrated as a generous pour in Scottish pubs and distilleries.
Capacity: 0.25 of a gill or 35.5ml
Dram (Avoirdupois)
A standard commercial mass unit equal to one-sixteenth of an avoirdupois ounce.
1.77 grams
Drift
A historic fleet measure representing a connected train of herring drift-nets stretching nearly a mile long.
Approx. 1 mile of nets
Ell
A traditional cloth-measuring length of 45 inches, descended from the arm-based measures of the medieval textile trade.
45 inches = 1.143 metres
Erg
The energy unit of the centimetre-gram-second system, being the work done by one dyne acting through one centimetre.
0.0000001 joules
Erw (Welsh Acre)
The Welsh acre, set out in the tenth-century Laws of Hywel Dda and defined by the reach of a ploughman’s goad rather than by a day’s work.
Approx. 4,320 square yards = 3,612 square metres
Faggot
A bound bundle of brushwood or small branches, customarily three feet in length and twenty-four inches in girth.
Approx. 0.09 cubic metres per bundle
Fahrenheit (°F)
The standard British temperature scale used across weather and daily life until the late 20th century.
Water freezes at 32°F and boils at 212°F
Fall (Scots Rod)
The Scots counterpart of the English rod, being six Scots ells, and the building block of both the Scots mile and the Scots acre.
Approx. 6.2 yards = 5.67 metres
Farad (F)
The SI unit of capacitance, named for Michael Faraday, measuring a conductor's ability to store electric charge.
1 Coulomb per Volt
Farthing (¼d)
A historic coin worth one-quarter of an old penny, withdrawn from circulation in 1960.
0.25 old pence ≈ £0.001 (modern)
Fathom (fm)
Derived from Old English for outstretched arms, traditionally used for measuring water depth.
6 feet = 1.8288 metres
Feet of Water (ftH₂O)
A traditional plumbing unit used to describe hydraulic head pressure.
2,989.07 Pascals
Feet per Minute (ft/min)
The working unit for slow mechanical motion in British industry, from colliery winding gear to lifts and conveyor belts.
0.00508 metres per second
Feet per Second (fps)
Historically used in British ballistics and engineering to measure projectile velocities.
0.3048 metres per second
Firkins
A quarter of a barrel equal to 9 imperial gallons, still utilised for cask ales.
9 imperial gallons = 40.91 litres
Firlot
A quarter of a Scots boll, and the everyday working measure of the Scottish grain market.
Approx. 36 litres for wheat; larger for oats and barley
Florin
Introduced in 1849 as an early decimal experiment worth one-tenth of a pound.
2 shillings = 10 new pence ≈ £0.10 (modern)
Fluid Drachm (fl dr)
One eighth of an imperial fluid ounce, used by apothecaries and chemists for compounding liquid medicines.
3.5516 millilitres
Fluid Ounce
One-twentieth of an imperial pint, distinctly larger than its US fluid ounce counterpart.
28.41 millilitres
Foot (ft)
A universal traditional length unit historically based on the human foot.
12 inches = 30.48 centimetres
Foot-pound (ft·lb)
The work performed in raising a weight of one pound through a vertical distance of one foot.
1.3558 joules
Fortnight
Derived from "fourteen nights," representing a standard period of two weeks.
14 days = 2 weeks
Fother
A traditional heavy weight measure derived from "cartload," standardised at roughly 2,240 pounds for bulk commodities like lead and coal.
Approx. 2,240 pounds
Furlong (fur)
Originally the length of a furrow in one acre of ploughed land; survives in horse racing.
220 yards = 201.168 metres
Furlongs per Fortnight
A playful composite speed unit used humorously to describe extremely sluggish velocities.
0.000166 mph
Gallon (gal)
The definitive imperial fluid measure standard equal to 4 quarts, still used for UK fuel efficiency metrics.
4.54609 litres
Gibibyte (GiB)
Exactly 1,073,741,824 bytes, being two to the power of thirty, and the binary counterpart to the decimal gigabyte.
1,073,741,824 bytes = 1.074 gigabytes
Gigabyte (GB)
A massive storage leap introduced into commercial computing when the first 1GB hard drive debuted in 1980.
1,000,000,000 bytes
Gill (gi)
One-quarter of a pint, traditionally used for measuring spirits and pub pour sizes.
142 millilitres
Gowpen
The hollow formed by two cupped hands, and the quantity they will hold.
Approx. 0.9–1.1 litres, varying with the hands
Grain (gr)
Based on the weight of a single barley grain, identical across avoirdupois, troy, and apothecary systems.
64.79891 milligrams
Grain of Wheat
An ancient natural unit of weight and capacity, variable by agricultural commodity.
Approx. 65 milligrams
Gravity
Used by British brewers to measure how dense unfermented beer was compared to pure water.
Specific gravity measurement
Great Gross
A master wholesale unit equal to twelve gross (1,728 units), used for micro-hardware like pins and nails.
1,728 units (12 gross / 144 dozen)
Groat
Reintroduced in the 1830s specifically to standardise hackney cab fares.
4 old pence ≈ £0.017 (modern)
Gross (gro)
A wholesale quantity representing a dozen dozens (144 units) for counting small goods.
144 units (12 dozen)
Guinea (gn)
Originally a gold coin, it evolved into a prestige unit of account worth 21 shillings.
1 pound 1 shilling ≈ £1.05 (modern)
Gurry
A large rectangular box on squat legs with long carrying poles fixed to each side, holding about six hundreds of pilchards.
6 hundreds = approx. 720 pilchards
Halfpenny (½d)
A historic British coin worth half of an old penny.
0.5 old pence ≈ £0.002 (modern)
Hand (hh)
Exclusively used to measure the height of horses from the ground to the withers.
4 inches = 10.16 centimetres
Hank
A fixed length of yarn rolled into a coil (840 yards for cotton, 560 yards for wool).
Cotton: 840 yards; Wool: 560 yards
Hectare (ha)
Ten thousand square metres, being a square of one hundred metres on each side, and the metric standard for agricultural land.
10,000 square metres = 2.4711 acres
Hectopascal (hPa)
The SI-conformant name for the millibar, adopted by meteorological services during metrication without altering any recorded value.
100 Pascals = 1 millibar
Hertz (Hz) - Audio
A frequency metric tracking physical compression wave cycles per second across the human hearing range.
Cycles per second
Hertz (Hz) - Electrical
Named after Heinrich Hertz, tracking alternating current wave cycles.
Cycles per second
Hide
A variable medieval land unit of approximately 120 acres, notionally sufficient to support a single peasant household.
Approx. 120 acres = 485,623 square metres
Historical Ale Gallon
A Tudor-era 282 cubic-inch measure for malt liquor, intentionally sized larger than wine measures to give working-class consumers a more generous pour per penny.
4.621 litres
Hogshead
A large traditional bulk shipping cask typically holding 54 gallons for wine and beer.
245.49 litres
Hoppus Foot (h ft)
The standard measure for round timber, derived from Edward Hoppus’s quarter-girth formula of 1736 and still used in tropical hardwood trading.
1 hoppus foot = 1.273 true cubic feet = 0.036 cubic metres
Hoppus Ton
Fifty hoppus feet, and the bulk unit in which round timber was shipped and invoiced.
50 hoppus feet = 63.7 true cubic feet = 1.8 cubic metres
Horsepower-hour (hph)
The total work performed by one mechanical horsepower sustained for a full hour.
2.685 megajoules
Human Hair Width
A common natural reference benchmark for microscopic measurements.
0.07 millimetres
Hundredweight (cwt)
The traditional "long hundredweight" of 112 lbs established legislatively by Edward III.
112 pounds = 50.8023 kilograms
Inch (in)
A traditional length unit historically derived from the width of a human thumb.
2.54 centimetres
Inches of Mercury (inHg)
Historically used in British meteorology and aviation to measure barometric pressure.
3,386.39 Pascals
Inches of Water (inH₂O)
A fine-grained pressure unit for very low pressures, used in gas supply, flue draught and ventilation work.
249.09 Pascals
Irish Acre
Seven thousand eight hundred and forty square yards, being the acre as reckoned on the Irish perch of seven yards.
7,840 square yards = 6,555 square metres = 1.62 English acres
Irish Mile
Two thousand two hundred and forty yards, the longest of the miles used across these islands.
2,240 yards = 2.048 kilometres = 1.27 English miles
Irish Perch
Seven yards, or twenty-one feet, against the English perch of five and a half yards.
7 yards = 21 feet = 6.4008 metres
Joule (J)
Named after James Prescott Joule, representing energy expended by an electric current.
1 Watt-second
Keel
An industrial weight unit equal to 8 Newcastle chaldrons, named after the flat-bottomed boats that ferried coal down the River Tyne.
21.54 tonnes
Kelvin (K)
The absolute thermodynamic temperature scale used in scientific and engineering research.
Absolute scale where 0 K = -273.15°C
Kibibyte (KiB)
Exactly 1,024 bytes, being two to the power of ten, and the binary counterpart to the decimal kilobyte.
1,024 bytes = 1.024 kilobytes
Kilderkin
An 18-gallon cask volume representing exactly half of a standard beer barrel.
81.83 litres
Kilobyte (KB)
One thousand bytes under the SI definition, though for decades it was used loosely to mean 1,024.
1,000 bytes
Kilometres per Hour (km/h)
The metric road speed standard across most of the world, including the Republic of Ireland since 2005.
0.621371 miles per hour
Kilopascal (kPa)
One thousand pascals, the practical metric working unit for everyday and structural pressures.
1,000 Pascals = 0.145 psi
Kilowatt-hour (kWh)
One kilowatt of power sustained for one hour, and the unit in which British electricity has been bought and sold since the earliest public supply.
3.6 megajoules
Knot (kn)
One nautical mile per hour, originating from counting knots on a ship’s log-line.
1.15078 mph
Lady Day
One of the four traditional Quarter Days in the British calendar, falling on March 25th.
March 25th
Lammas
An ancient British harvest festival and traditional Scottish term day falling on August 1st.
August 1st
Last (Fisheries)
A medieval wholesale volume metric equal to 12 packed fish barrels or up to 12,000 individual herrings.
Approx. 10,000 - 12,000 fish
Last (Weight)
A traditional medieval wool trade bulk unit representing 12 packs and over 4,000 pounds.
>4,000 pounds
Lea
A smaller subdivision of a hank used in textile mills (120 yards for cotton).
Cotton: 120 yards (109.7 metres)
League
An ancient unit representing the estimated distance a person could walk in one hour.
3 miles = 4.828 kilometres
League per Hour
Found in older British literature to describe the steady speed of a walking pace.
3 mph
Ligne
A fine measure of diameter surviving in two distinct trades, at two quite different sizes.
Watchmaking: 2.2558 mm. Buttons: 0.635 mm (1/40 inch)
Link (lk)
Derived from Gunter’s surveying chain, where 100 links equal one chain (7.92 inches each).
7.92 inches = 0.201168 metres
Load (Timber)
The customary cart-load of timber, being fifty cubic feet of squared baulks or forty cubic feet of round logs.
Squared: 50 cu ft = 1.42 m³. Round: 40 cu ft = 1.13 m³
London Chaldron
A dry volume measure equal to 36 bushels, tightly enforced at the Port of London to regulate domestic coal shipments.
Approx. 1,309 litres
Long Hundred / Great Hundred
An old Germanic counting convention where a "hundred" officially meant 120.
120 units
Mach Number
Used in British aerospace to measure the ratio of speed to the local speed of sound.
Speed of sound (approx. 761 mph at sea level)
Mark
A medieval unit of account representing exactly two-thirds of a pound sterling.
13 shillings 4 pence ≈ £0.67 (modern)
Martinmas
A traditional Scottish legal term day marking the conclusion of the agricultural year on November 11th.
November 11th
Maund
A stout two-handled wicker basket holding three hundreds of pilchards, and the working measure of the Cornish seine fishery.
3 hundreds = approx. 360 pilchards, 50–55 lb
Mease (Maze or Maise)
A traditional bulk count for herring standardised at 500 fish.
500 fish
Mebibyte (MiB)
Exactly 1,048,576 bytes, being two to the power of twenty, and the binary counterpart to the decimal megabyte.
1,048,576 bytes = 1.049 megabytes
Megabyte (MB)
A unit of digital information representing roughly one million bytes.
1,000,000 bytes
Metres per Second (m/s)
The standard SI unit used globally in scientific physics calculations.
2.23694 mph
Michaelmas
One of the four traditional Quarter Days in the British calendar, falling on September 29th.
September 29th
Midsummer
One of the four traditional Quarter Days in the British calendar, falling on June 24th.
June 24th
Mile (mi)
Standardised to exactly 5,280 feet by the English Parliament in 1593.
1,760 yards = 1.60934 kilometres
Miles per Hour (mph)
The enduring legal standard for all British road signs and vehicle speedometers.
1.60934 km/h
Millibar (mbar)
Formerly standard for UK weather forecasts, numerically identical to hectopascals.
100 Pascals
Millimetres of Mercury (mmHg)
The height a column of mercury rises under a given pressure, and still the worldwide standard for reporting blood pressure.
133.32 Pascals
Minim
The smallest fluid volume block in apothecary tracking, historically roughly one drop of medicine.
0.059 millilitres
Moment
A medieval time unit from chronologist Bede dividing an hour into 40 parts (90 seconds).
90 seconds
Nail
The finest subdivision of the cloth trade, being two and a quarter inches, or one sixteenth of a yard.
2.25 inches = 5.715 centimetres
Nautical Mile (nmi)
Based on Earth’s circumference, equal to exactly one minute of latitude.
1.15078 statute miles
Newcastle Chaldron
An industrial shipping measure optimised for northeastern coal carts and river barges, roughly double the London variant.
Approx. 2,618 litres
Newton Scale (°N)
One of the earliest numbered temperature scales, devised by Isaac Newton around 1700 using linseed oil as the working fluid.
1°N = 3.03°C
Nibble
A four-bit computing unit (half a byte) coined to represent a single hexadecimal digit.
4 bits
Noble
An official gold coin introduced by Edward III in 1344 worth one-third of a pound.
6 shillings 8 pence ≈ £0.33 (modern)
Octave
A structural cooperage masterpiece holding exactly one-eighth of a standard barrel.
50 Litres (Cask)
Ohm (Ω)
The SI unit of electrical resistance, named for Georg Simon Ohm, whose 1827 work established the relationship between voltage, current and resistance.
1 Volt per Ampere
Oxgang / Bovate
The share of land attributed to a single ox within an eight-beast plough team, being one eighth of a carucate.
Approx. 15 acres = 60,703 square metres
Pace
A traditional length unit representing a full two-step stride (5 feet).
5 feet = 1.524 metres
Pack (or Sack)
A traditional wool trade bulk unit representing two weys (240 to 364 pounds of fleece).
240-364 pounds
Pad (Fish)
A lidded wicker basket holding half a hundred of mackerel, being seven to eight stone of fish, and the standard unit of the Newlyn mackerel trade.
Half a hundred = 60 mackerel, approx. 98–112 lb
Pascal (Pa) - Acoustic
A unit measuring microscopic atmospheric pressure deviations exerted by passing audio waves.
Newtons per square metre (N/m²)
Pascal (Pa) - Pressure
The standard SI pressure unit representing one Newton per square metre.
1 Newton per square metre
Pebibyte (PiB)
Exactly 1,125,899,906,842,624 bytes, being two to the power of fifty, and the binary counterpart to the decimal petabyte.
1,125,899,906,842,624 bytes = 1.126 petabytes
Peck (pk)
A traditional dry volume market unit equal to 2 gallons for orchard fruits.
9.09 litres
Penny (d)
The historic coin whose abbreviation "d" derives from the Roman denarius.
1 old penny ≈ £0.004 (modern)
Pennyweight (dwt)
A traditional troy weight unit equal to 24 grains or one-twentieth of an ounce.
1.56 grams
Perch
A traditional land surveying unit (16.5 feet / 5.5 yards), synonymous with Pole and Rod.
16.5 feet = 5.0292 metres
Perch (Channel Islands)
A fortieth of a vergée, and the working subdivision of Channel Islands land measurement.
Jersey: approx. 44.7 m². Guernsey: approx. 39.4 m²
Petabyte (PB)
One quadrillion bytes, being a thousand terabytes, and the working unit of large-scale data storage.
1,000,000,000,000,000 bytes = 1,000 terabytes
Petrograd Standard
One hundred and sixty-five cubic feet of sawn softwood, and the standard measure of the Baltic timber import trade.
165 cubic feet = 4.672 cubic metres
Phon
A psychoacoustic metric mapping human perception of loudness across different frequencies.
Equal-loudness level contour unit
Pilchard Hogshead
The export cask of the Cornish pilchard trade, originally 52 gallons and later described in legislation as 50, holding three thousands of pressed pilchards.
448 lb net, 476 lb gross. Nominally 3,600 fish, in practice 2,500–4,500
Pin
Four and a half imperial gallons, being half a firkin, and the smallest standard cask in the British brewing trade.
4.5 imperial gallons = 20.46 litres = 36 pints
Pinch
As much of a dry substance as can be taken up between the thumb and forefinger.
Conventionally 1/8 teaspoon = approx. 0.6 millilitres
Pint (pt)
20 fluid ounces. The iconic pub baseline fluid measure for British draught beer.
568.26 millilitres
Pole
A traditional land surveying unit (16.5 feet), synonymous with Perch and Rod.
16.5 feet = 5.0292 metres
Poppyseed
An ancient microscopic length unit defined as one-quarter of a barleycorn.
1-2 millimetres
Pot (Fish)
An undefined trawl-fish measure recorded at Folkestone in the 1830s, used alongside the pad.
Undefined; 3 pots to a pad, but 2 pots to a half-pad
Poundal (pdl)
The imperial unit of force, being that which accelerates a mass of one pound at one foot per second squared.
Approx. 0.13825 newtons
Pounds per Square Foot (psf)
Used in older British structural engineering to describe building floor loads.
47.88 Pascals
Pounds per Square Inch (psi)
The common imperial pressure unit for everyday applications like car tyres.
6,894.76 Pascals
Proof
Traditional spirit strength verified by whether gunpowder soaked in alcohol would ignite.
57.1% ABV (at 100° UK Proof)
Puncheon
An 84-gallon wide-bellied traditional bulk shipping cask used for rum and wine storage.
381.87 litres
Quarantine
A traditional 40-day legal period originating from medieval isolation rules for incoming vessels.
40 days
Quarter (qr)
A quarter of a hundredweight, being 28 pounds or two stone, and a working tier of the coal and produce trades.
28 pounds = 12.7006 kilograms
Quarter Cask
A small cask holding exactly one-quarter of a standard barrel, engineered for rapid maturation.
125 Litres (Cask)
Quarter Cran
One quarter of a cran, made a legal measure for the fresh herring trade by the Cran Measures Act of 1908.
9.375 imperial gallons = 42.6 litres
Queen Anne Wine Gallon (1707)
A 1707 statutory standard established to resolve maritime customs disputes, which later crossed the Atlantic to become the standard US Fluid Gallon.
3.785 litres
Quire
One-twentieth of a ream, historically fluctuating between 24 and 25 sheets of loose paper.
24 or 25 sheets
Rankine (°R)
An absolute temperature scale using Fahrenheit-sized degrees, proposed by the Glasgow engineer William John Macquorn Rankine in 1859.
Absolute scale where 0°R = -459.67°F
Ream
A staple paper trade measure evolving through 480 and 500-sheet standards to account for press wastage.
480 to 500 sheets
Réaumur (°Ré)
A scale devised by René Antoine Ferchault de Réaumur in 1730, setting the freezing point of water at 0 and its boiling point at 80.
1°Ré = 1.25°C
Rod
A traditional surveying length (16.5 feet), synonymous with Perch and Pole.
16.5 feet = 5.0292 metres
Rømer (°Rø)
A scale created by the Danish astronomer Ole Rømer in 1701, setting a brine freezing mixture at zero and body temperature near 22.5.
1°Rø = 1.905°C
Rood
One-quarter of an acre, traditionally used for measuring small land plots and gardens.
1,011.71 square metres
Rundlet
A small British wine cask holding precisely 18 Queen Anne wine gallons, favoured for transporting premium fortified wines.
68.14 litres
Schooner
Two thirds of an imperial pint, and the newest legal measure for draught beer in Britain.
2/3 imperial pint = 379 millilitres
Score (Quantity)
The classic British counting unit of 20, historically tracked by carving notches into wooden tally sticks.
20 units
Score (Time)
A traditional vigesimal score unit of time equivalent to a period of 20 years, frequently used historically to track generations and eras.
20 years
Scots Ell
Scotland’s standard ell, running to about 37 inches, and the unit from which the fall, mile and acre were all derived.
Approx. 37 inches = 94 centimetres
Scots Mile
Scotland’s own mile, running to about 1,976 yards, appreciably longer than the English statute mile.
Approx. 1,976 yards = 1,807 metres
Scots Pint
Scotland’s own pint, holding roughly 1.7 litres, or about three imperial pints. Its physical standard was the Stirling Jug, held by the burgh of Stirling.
Approx. 1.696 litres = 2.98 imperial pints
Scruple (℈)
A tiny apothecary mass unit equal to exactly 20 grains, used by chemists to weigh powdered medicinal ingredients.
20 grains = 1.296 grams
Seam
A traditional packhorse load measure for commodities like glass and wool (200-300 lbs).
200 to 300 pounds
Sennight
Derived from "seven nights," representing a precise week-long period in older legal texts.
7 days
Sherry Butt
The heavyweight champion of cask ageing, historically seasoned to impart rich dried-fruit notes.
500 Litres (Cask)
Shilling (s)
Equivalent to 12 pence, commonly referred to colloquially as a "bob".
12 old pence ≈ £0.05 (modern)
Sixpence
A historic British silver coin worth six pence, famous for wedding folklore.
6 old pence ≈ £0.025 (modern)
Slug
The imperial unit of mass, defined as that which one pound of force accelerates at one foot per second squared.
Approx. 14.594 kilograms = 32.174 pounds
Sovereign
A prestigious British gold coin with a nominal value of one pound sterling.
1 pound ≈ £1.00 (modern)
Span
An ancient length unit measuring the distance from thumb to little finger on a spread hand (9 inches).
9 inches = 0.2286 metres
Speed of Light (c)
The ultimate cosmic speed limit used in foundational physics wave propagation calculations.
299,792,458 metres per second
Spool
A traditional commercial unit of length used primarily for heavy linen and hemp yarn, representing 1,440 yards (12 leas) of wound material.
1,440 yards (12 leas)
Spyndle
A major wholesale unit of length used in early industrial spinning mills, representing 14,400 yards (48 leas) of wound thread.
14,400 yards (48 leas)
Square Mile (mi²)
The largest customary imperial area unit, containing exactly 640 acres.
640 acres = 2.59 square kilometres
Square Perch
The square of a perch of 16½ feet, being 30¼ square yards. Forty square perches make one rood.
30¼ square yards = 25.29 square metres
Stack (Wood)
One hundred and eight cubic feet of stacked wood, being the customary British firewood measure.
108 cubic feet = 3.06 cubic metres
Standard Coal Sack
A retail street trade bag legally defined as one hundredweight (112 lbs) to prevent consumer short-measuring.
112 pounds = 50.802 kilograms
Stave
A riven oak board shaped for cask-making, graded and traded by the size of vessel it was cut for.
Varies by grade; a hogshead stave typically 36–42 inches long
Stick
A processing measure consisting of 25 fish threaded onto a wooden spit for hanging in smokehouses.
Approx. 25 fish
Stone (st)
The traditional British weight unit equal to 14 pounds, remaining the enduring colloquial choice for measuring personal human body weight.
14 pounds = 6.35029 kilograms
Sulung
The Kentish unit of land assessment, reckoned at roughly two hides, and divided into four yokes.
Approx. 240 acres = 97 hectares
Swill
An East Anglian wicker basket with multiple handles, used to land herring and holding one-third of a cran.
Approx. one third of a cran
Tebibyte (TiB)
Exactly 1,099,511,627,776 bytes, being two to the power of forty, and the binary counterpart to the decimal terabyte.
1,099,511,627,776 bytes = 1.1 terabytes
Ten
A massive Northern English colliery volumetric standard used to calculate landowner mining royalties, equal to roughly 22 keels.
Approx. 22 keel
Terabyte (TB)
A massive modern unit representing a trillion bytes of digital storage.
1,000,000,000,000 bytes
The Analytical Engine
Charles Babbage's grand mechanical computing design that anchors modern digital conversions.
Data Unit Calculator
Therm (thm)
Exactly 100,000 British Thermal Units, adopted as the standard billing unit for gas supply across Britain.
100,000 Btu = 29.31 kilowatt-hours
Thimbleful
An archaic, colloquial measure of liquid capacity corresponding to the small volume of a sewing thimble, roughly equivalent to a fluid dram or teaspoon.
Approx. 3.5 millilitres
Thou / Mil
One-thousandth of an inch, heavily relied upon in manufacturing for precision component metrics.
0.001 inches = 0.0254 millimetres
Thousand (Pilchards)
Ten long hundreds of pilchards, being 1,200 fish rather than a thousand.
1,200 fish, being 10 long hundreds of 120
Threepence
A historic British coin worth 3 pence, affectionately known as the "threepenny bit."
3 old pence ≈ £0.0125 (modern)
Thumb
The width of a thumb at the knuckle, taken as roughly one inch, and the body measure from which the inch descends.
Width approx. 2–2.3 cm; top joint approx. 2.5 cm
Tierce
A traditional wine cask holding 42 Queen Anne wine gallons, whose exceptional transit stability inspired the modern oil barrel.
158.99 litres
Timber
A fur trade unit designating a bundle of 40 pelts, commonly used for luxury furs like ermine.
40 pelts
Tod
A historical English wool trade weight unit equal to two stone.
28 pounds = 12.7006 kilograms
Ton (long ton)
The traditional British long ton containing exactly 2,240 pounds.
2,240 pounds = 1,016.047 kilograms
Troy Ounce (ozt)
The precious metal ounce of 480 grains, descended from the weights used at the medieval fairs of Troyes in Champagne.
480 grains = 31.1035 grams
Troy Pound (lb t)
The precious metal pound of twelve troy ounces, or 5,760 grains, and the standard by which English coin was struck after Henry VIII abandoned the Tower pound in 1526.
5,760 grains = 373.24 grams
Truss
A bound bundle of hay or straw, with three distinct weights fixed in law: 60 pounds for new hay, 56 for old, and 36 for straw.
New hay 60 lb = 27.2 kg. Old hay 56 lb = 25.4 kg. Straw 36 lb = 16.3 kg
Tun
The largest traditional English cask, holding 252 wine gallons, and the origin of a ship’s tonnage.
252 wine gallons = 953.9 litres
Vergée
The traditional land measure of Jersey and Guernsey, descended from Norman French practice and still in current use.
Jersey: approx. 0.44 acres = 1,786 m². Guernsey: approx. 0.39 acres = 1,576 m²
Virgate
A variable medieval unit (approx. 30 acres) ploughed by a team of two oxen.
121,400 square metres
Volt (V)
Tracks electric potential pressure pushing current through an electrical circuit.
1 Joule per Coulomb
Warp
A rapid dockside counting tally of exactly four fish, born from the ergonomics of grabbing two fish in each hand.
Exactly 4 units
Watt (W)
Calculates structural power expenditure matching Volts multiplied by Amperes.
1 Joule per second
Watt-hour (Wh)
One watt of power sustained for one hour, being one thousandth of a kilowatt-hour.
3,600 joules
Wey
A traditional heavy British bulk weight unit used for commodities like wool and salt.
Wool: 182 pounds = 82.55 kilograms
Whitsunday
A traditional Scottish term day marking the financial and agricultural midpoint of the year.
May 15th (Fixed Scottish Term Date)