BWMA have this helpful guide to show how straightforward Imperial measurements are:

*Despite the fact that imperial units of measurement are still in widespread use in the UK, the USA and many other countries, most young people in Britain today are not taught how to use them. To remedy that, the BWMA has put together the following guide to teach the most basic and commonly used units.*

**Length**

The basic unit of length is the inch. There are 12 inches in a foot. This means that a foot can easily be divided by 2, 3, 4 or 6 to give a round number: one third of a foot is 4 inches, one quarter of a foot is 3 inches, half a foot is 6 inches, and so on. Feet and inches are sometimes expressed with a prime and double prime (inverted commas), so 3 foot 6 inches can be expressed as 3′ 6″. This is often seen on road signs.

There are 3 feet in a yard, or 36 inches. So:

1 yard = 3 feet = 36 inches

1/2 yard = 1 foot 6 inches = 18 inches

1/3 yard = 1 foot = 12 inches

1/4 yard = 9 inches (3/4 of a foot)

1/6 yard = 6 inches (1/2 of a foot)

The inch is typically divided into fractions of one sixteenth for measuring very small lengths. This means it can also be expressed in halves, quarters and eighths of an inch.

The other main units of length after the yard are the chain, furlong and mile. There are 22 yards in a chain, 10 chains in a furlong and 8 furlongs in a mile. This means that:

1 chain = 22 yards = 66 feet

1 furlong = 10 chains = 220 yards = 660 feet

1 mile = 8 furlongs = 80 chains = 1760 yards = 5280 feet

This means that there is a unit for every size of distance people may need to measure in different situations. Feet and inches are used for human heights, yards are used for road sign distances, chains are used for railway measurements, furlongs for measuring fields and horse races, and miles for the distances between towns and cities. There is rarely ever a need to convert directly from miles to yards; the chain and furlong fit in between to give an appropriate unit for each kind of distance.

**Area**

An acre is an area equivalent to one chain by one furlong, or 22 by 220 yards. This means an acre can easily be divided up into 8 square chains, each of which can be divided into 484 square yards (giving 4840 square yards in an acre). Ten acres make a square furlong, and 64 of these (8×8 in a grid), or 640 acres, make a square mile.

**Weight**

The main imperial weights you will encounter in day-to-day life are the ounce (oz), pound (lb) and stone (st). 16 ounces are in a pound, allowing division by 2, 4 and 8. The stone provides a unit ideally sized for human weights in between the pound and the next unit up, the hundredweight (cwt). There are 14 pounds in a stone and 8 stones in a hundredweight, meaning there are 112 pounds in a hundredweight. The last unit above that is the ton, which has 20 hundredweight or 2240 pounds.

With no irony at all, it acually highlights that imperial measurements are largely inaccurate and pre-industrial.

A sixteenth of an inch for measuring "very small lengths". In reality, very small lengths ended up being measured in thousandths of an inch or ridiculous sizes like 9/64ths of an inch. This is a list of HSS drill sizes in imperial by size:

1/16, 5/64, 3/32, 7/64, 1/8, 9/64, 5/32, 11/64, 3/16, 13/64, 7/32, 15/64, 1/4, 17/64 and so on. Intuitive? is it fuck.

But of course it's crucial that kids today need to know that an acre is the area that could be ploughed in a day with a horse - one 'furrow long' by a chain...

And it's mad the way they skip from how great it is that a foot can be divided into 12 inches giving 4 x 3 inches and 2 x 6 inches or 3 x 4 inches, but that goes by the board for the puond which is divisible by 16. No mention at all of the usefulness of a stone being divisible by... er... fourteen.

They're right that these ancient measurements were all based on things that were readily available and to hand (a hand = four inches for measuring horses) but we no longer measure water depths with a bit of rope or an inch with the top joint of our thumbs.

And having big units for big things and little units for little things maks asolute sense, but it also makes sense if the big units are easilly converted. 1cm = 10mm, 1m = 1000mm, 1km = 1000m... Kilos and grammes do the same job as pounds and ounces, litres and millilitres do the same as pints and fluid ounces...