Units You Are Still Using Without Realising
Britain went metric in the 1970s. Nobody told the shoe trade, the racecourse, the gas board or the global oil market.
Hiding in plain sight
These are not historical curiosities. They are measurements you encountered this week, wearing a disguise.
The barleycorn
Your shoe sizeEdward II fixed the inch in 1324 as three grains of barley end to end. Shoe sizes still advance by exactly one barleycorn, a third of an inch, per size. A size 9 foot is a third of an inch longer than a size 8, and has been since the fourteenth century.
Read the full entry →The chain
Every cricket pitchEdmund Gunter devised a 66-foot surveying chain in 1620 because it made acreage arithmetic simple: ten square chains to the acre. The pitch between the wickets was set to one chain, and it has never moved. Every ball bowled in the history of the game has travelled a surveyor’s instrument.
Read the full entry →The furlong
Horse racingA furrow long: the distance an ox team could plough before needing to turn. Eight of them make a mile, which is why the mile has its awkward 5,280 feet. British racecourses still mark distances in furlongs, so a two-mile race is measured out in ploughing.
Read the full entry →The hand
Horses, stillFour inches, originally a palm’s width, and the one body measure that never gave way to the metric system. Note the notation: a horse of 16.2 hands is sixteen hands and two inches, not sixteen point two. Get that wrong at a sale and you will be corrected.
Read the full entry →The troy ounce
The price of goldEvery gold price quoted anywhere in the world is per troy ounce of 480 grains, not the avoirdupois ounce of 437.5 that weighs your post. Which is why a pound of gold is lighter than a pound of feathers, while an ounce of gold is heavier than an ounce of feathers.
Read the full entry →The therm
Your gas billA hundred thousand British Thermal Units, and the Btu is defined by raising a pound of water one degree Fahrenheit. Your gas meter reads volume, the supplier converts it to therms, then to kilowatt-hours. A Victorian imperial unit sits quietly in the middle of a modern utility bill.
Read the full entry →The tun
The size of shipsMedieval customs duty was charged on how many tuns of wine a vessel could carry, so ships were described by their tunnage. The spelling drifted, the meaning shifted, and every modern vessel measured in gross tonnage is still, distantly, being described in casks of wine.
Read the full entry →The tierce
The oil barrelA 42-gallon wine cask that proved unusually stable in a rolling ship’s hold. When the Pennsylvania oil trade needed a standard container in the 1860s, coopers already knew how to make one that size. The global oil price is quoted per barrel because of a wine cask.
Read the full entry →Phrases that used to be arithmetic
Every one of these was a precise quantity before it became a turn of phrase.
A baker’s dozen
Under the Assize of Bread, short-weight loaves brought fines or the pillory. Since flour moisture and oven heat were unpredictable, bakers added a thirteenth loaf as insurance against their own ovens.
Read the full entry →Four score and seven
A score is twenty, from the notch scored into a tally stick at every twentieth count. Lincoln was not being poetic so much as using the accounting language of his day.
Read the full entry →Quarantine
From the Italian quaranta giorni. Ships arriving in Venice during the plague were held at anchor for exactly forty days. The word is a measurement that outlived its measure.
Read the full entry →A fortnight
Fourteen nights. Its forgotten sibling is the sennight, seven nights, which is what the English called a week until the word quietly fell out of use.
Read the full entry →Hiding your light under a bushel
A bushel was eight gallons of dry goods, and the vessel that measured it was a wooden tub large enough to put over a lamp. The metaphor only works if you know the container.
Read the full entry →Worth its weight in gold
Weighed in which pound, though? The troy pound of 5,760 grains, or the avoirdupois pound of 7,000? English merchants ran both at once for centuries, and the distinction was worth real money.
Read the full entry →Gloriously absurd, entirely real
Units that sound invented. Every one of them was in genuine use, and two still are.
Furlongs per fortnight
A real calculation and a deliberate joke, used by lecturers to prove that dimensional analysis works however silly the units. It comes to roughly one ten-thousandth of a mile per hour, which is about the speed of a growing fingernail.
Read the full entry →The double-decker bus
Twelve tonnes, and the unit British journalists reach for whenever a number gets too large to picture. Nobody agreed to this. It simply happened, and it has now been happening for the better part of a century.
Read the full entry →The clove
Seven pounds, half a stone, and the weight of a single medieval fleece. Wool and cheese were traded by the clove for centuries, which means the English once had a dedicated unit for the amount of wool on one sheep.
Read the full entry →The warp
Exactly four fish. A dockside tallyman could pick up two herring in each hand, so four became a counting unit. Manual ergonomics, promoted to arithmetic.
Read the full entry →The poppyseed
A quarter of a barleycorn, so a twelfth of an inch, and the smallest unit medieval English law bothered to name. When you needed to be precise about something very small, you reached for a seed.
Read the full entry →The moment
Ninety seconds. Bede divided the hour into forty of them, so a medieval moment was a precise chronological quantity rather than a figure of speech. "Wait a moment" was once an actionable instruction.
Read the full entry →Two hundred more where these came from
The archive holds every unit on this page and a great many stranger ones: the chaldron, the oxgang, the swill, the spyndle and the Angels’ Share.