I’m sorry, but there is really no way to make this interesting. In my novels the characters talk about how far they’ve travelled, how much things weigh and how much ale is left in a barrel. In order to do this convincingly, they can’t talk about kilometres, kilogrammes and litres. It turns out that they can talk about feet, yards and miles, though, which is a relief.
Measurements were starting to become standardised in the fourteenth century. Weights were supposed to be standardised to what was used in Winchester, but many towns retained their local weights and measures. I can see that there might have been some very great misunderstandings when people from different parts of the country had dealings with one another.
These are the most common medieval weights and measures:
Furlong – the length of a furrow of a field ploughed by a team of eight oxen. It was forty perches or 220 yards. This was the long side of the acre. The other side was 22 yards.
League – approximately three miles.
Mile – there were officially two different miles. One was the statute mile and the other was the Old French mile, which is 1.25 statute miles. There were also, of course, local miles of varying lengths. The length of a mile wasn’t fixed formally until the end of the sixteenth century.
Rod/perch/pole – five and a half yards.
Ell – used for measuring cloth. It was usually forty-five inches, but could be twenty-seven inches for Flemish cloth. The ruler used for measuring cloth was known as an ell-wand.
Foot – twelve inches.
Inch – the French word for inch will help us here. It’s ‘pouce’, which also means thumb. An inch was the width of an adult thumb.
Yard – three feet, but originally the length of an outstretched arm. Henry I is supposed to have used his own arm as the standard.
Bushel – eight gallons.
Chaldron – 36 bushels.
Hundredweight – 112lb except in Devon, where it was 120lb.
Pound (lb) – 16 ounces (oz), except in Devon, where it was 18oz.
Quarter (or core) – eight bushels. It was used for weighing grain.
Stone – 14lb, except in Devon, where it was 16lb.
Gallon – varied depending on whether it was ale or wine being measured.
Hogshead – sixty-three wine gallons, fifty-two-and-a-half ale gallons. In London it was usually forty-eight ale gallons.
Acre – the amount of land a team of 8 oxen can plough in a day.
Ploughland – the amount of land a team of 8 oxen can plough in a year.
Both of these will clearly vary greatly across the country. An acre in Norfolk will be larger than an acre in Yorkshire or Devon simply because Norfolk is flatter and easier to plough. Edward I tried, and failed, to standardise the size of an acre.
Rood – quarter of an acre.
You’ll have noticed that some of these measurements are almost meaningless. It’s all very well knowing that a bushel is eight gallons, but what was a gallon?
Apart from allowing my characters to discuss their journeys and the amount of land they hold, why is this important? Imagine you’re a merchant travelling from one market to another to sell your wares. You need to know what the units of measurement are in the towns you visit regularly. You will be accused of short-changing your customers if their expectations of what a bushel is exceed what you give them.
The Time Traveller’s Guide to the Fourteenth Century – Ian Mortimer
A Dictionary of Medieval Terms and Phrases – Christopher Corèdon with Ann Williams