I'm not the person you were replying to, but I can answer this one. And yeah, I can see all the metric fanboys (a very small subset of metric users, mind you) hovering over that downvote button, but I don't get paid in Internet points so here goes:
The nice thing about imperial (as well as the customary system used in the US) is that it's based on measurements that people have found useful over thousands of years. They're human units, adapted to what people need to do with them, not the other way around.
It's difficult to explain to metric folks because it's really something you have to experience. But here's an example:
Reservoir volume in the US is measured in acre-inches. An acre is a unit of area used for measuring property, usually farmland. It's a bit less than half of a hectare. And of course an inch is 2.4cm. Acre-inches sounds totally bizarre when you first hear about it. But for the people that need to work with this value, it's an extremely useful way to measure reservoirs and gives you an intuition that you just don't get from cubic meters.
It's true that you can't just convert that to other units of volume without doing some math or looking up the conversion rate, but that rarely matters. If you're trying to figure out how fast the lake will rise or fall with a given inflow and outflow, you're going to have to have some way to account for the fact that the lake is a) an irregular shape and b) takes up more area the higher the water gets. You already need to know the area of the lake at any particular height to work out the evaporation rate anyway, so that's a number you're going to have. The units are designed to make that calculation easier, which was really important back in the days when slide rules were the state of the art.
All the customary units are like this in one way or another. They're units designed for a particular domain, and when used in their domain they work very well and calculations can be done in your head. They use fractions because that's what people have historically used (seriously - my grandfather could work fractions in his head faster than I could type them into a calculator, and he made asphalt for a living. Imagine what a carpenter could do.).
Think about it. Imagine you were never taught a measurement system. You find yourself needing to come up with a unit to make measurements for wooden planks you're going to use to build a house. Would you choose a unit as long as a meter? Or one as short as a centimeter or even a decimeter?
Bonus challenge to the fine folks clicking that downvote button: give me a real practical reason to prefer Celsius to Fahrenheit, besides the fact that Celsius is part of the metric system. No, the freezing and boiling points of water don't cut it - I work with hydrocarbon fuels, I salt my driveway and patio, I don't live at sea level, and quite honestly every American 8-year-old can spout off 32° and 212°. There's a Fahrenheit equivalent to Kelvin (Rankine) so the Kelvin to Celsius equivalence doesn't count either. My claim is that both scales are completely arbitrary, and only advantage one has over the other is that you're used to one of them. Go ahead, prove me wrong!
> Reservoir volume in the US is measured in acre-inches.
Never heard of an acre-inch before, and I'd have to get out a calculator to work out how much water that actually is in pints or gallons, or how much it weighs.
The metric equivalent would be a hectare-meter or a hectare-mm. I know a hectare is 100 m x 100 m, so 10,000 m². So I instantly know that a hectare-meter is 10,000 m³ (10 ML, or 10,000 tonnes of fresh water). A hectare-mm is 10 m³ (10 kL). If my 1 ha block gets 1 mm of rain, then that's 10 kL or 10 tonnes of water. So easy i can do it in my head.
> And of course an inch is 2.4cm
2.54 cm.
A couple more to add to your list: an inch is about as long as your thumb joint (with some variation between individuals obviously). It's an easy way to gauge the size of everyday objects without needing to carry around a tape measure.
The recommendation for emergency supplies is about a gallon of water per person per day - or 3.7 liters if you're using metric.
I've also heard it claimed that the 0-100 Fahrenheit scale is more functionally useful because the endpoints of 0 and 100 represent the tipping point of serious danger for humans from hot or cold weather. The closer you get to 100 degrees the more care you need to take about heat stroke and keeping hydrated, and similarly the closer you get to 0 degrees the more care you need to take about retaining heat and staying out of the elements - the freezing and boiling point of water isn't a necessary marker for survival. And people like nice round numbers to serve as markers for such things, divisibility be damned.
Metric is sterile and functional for calculation and consistency, which is fine and necessary for many things, but that's not a reason to completely ditch Imperial.
> The nice thing about imperial (as well as the customary system used in the US) is that it's based on measurements that people have found useful over thousands of years. They're human units, adapted to what people need to do with them, not the other way around.
US customary is not "thousands" of years; temperature (Fahrenheit) only came out in 1724 for example, and many other units were only standardize much more recently:
* https://en.wikipedia.org/wiki/History_of_measurement#History...
* https://en.wikipedia.org/wiki/System_of_units_of_measurement...
Second, even with-in the system itself there was also sorts of inconsistencies. Until just a few years ago there were two "foot" units; one was recently retired:
* https://www.nist.gov/pml/us-surveyfoot
Here's another one: which weighs more, a pound of feathers or a pound of gold? A pound of feathers. Because feathers use one 'pound-system' [1] and is 453g, while gold uses another pound-system [2] and is 373g. But of course an "ounce" of gold (31g) is more than an "ounce" of feathers (28g), because Troy is 1/12 of pound but Avoirdupois is 1/16. In addition to the above "ounces" there is also "fluid ounces". And let's not forget about the third system [3], which got replaced by… the metric system in 1971.[4]
[1] https://en.wikipedia.org/wiki/Avoirdupois
[2] https://en.wikipedia.org/wiki/Troy_weight
[3] https://en.wikipedia.org/wiki/Apothecaries'_system
[4] https://en.wikipedia.org/wiki/United_States_Pharmacopeia
Also:
* https://en.wikipedia.org/wiki/Pound_(mass)
* https://en.wikipedia.org/wiki/Pound_(force)
> Think about it. Imagine you were never taught a measurement system. You find yourself needing to come up with a unit to make measurements for wooden planks you're going to use to build a house. Would you choose a unit as long as a meter? Or one as short as a centimeter or even a decimeter?
Millimeters. That single unit gets you down to very small scales (finer than 1/16") and to large lengths: four significant digits (9999mm) gets you to the equivalent of >32' (~11yd).
* https://web.archive.org/web/20200516223819/https://themetric...
As evidence for this Australia/NZ/EU do everything in millimetres in construction.
> US customary is not "thousands" of years
You misunderstood me. It's based on measurements that people have been using for thousands of years. The Romans had feet and miles, for example - not exactly the same lengths, but for the same purposes. The Japanese shaku is almost exactly the same as a US foot. A Japanese Shō is about half a gallon. A Chinese jīn is just slightly larger than a pound. There's a reason for this.
> there was also sorts of inconsistencies
I never claimed otherwise. But do notice that the survey foot and standard foot weren't used for the same purposes, and the difference between them wasn't likely to confuse anyone except maybe people new to the field.
> Here's another one: which weighs more, a pound of feathers or a pound of gold?
Yep, Troy weights. And no one's sure where the Troy system came from. The main reason for its use is because of international trade. Also not something regular people (i.e. people that didn't work directly with precious metals) would have had contact with.
> Millimeters
Hah! Yeah right. Look at all the various non-metric systems that have existed throughout history. Did any of them use something like millimeters to measure wooden planks? Why not?
> As evidence for this Australia/NZ/EU do everything in millimetres in construction.
They do it because the metric system is mandated there and it doesn't give you reasonably sized unit for that scale of work.
Try this: go to a home center (or whatever it's called there - the place you buy building supplies) and measure some drywall. Do the measurements you made agree to the advertised ones within half a millimeter? Compare the dimensions of drywall sheets from different pallets and manufacturers. Do their dimensions agree to within half a millimeter? If not, that's a sure sign you're using units poorly adapted for purpose.