Sure, so Imperial units aren’t like one set of cohesive measurements, they are based on units of measure that can be easily estimated without a measuring tool. A foot is about the length of a foot. A cup is a cup. A mile is a thousand paces. 0 degrees Fahrenheit was the coldest outside temperature in the place where Fahrenheit lived, and 90 was the temp of a human body.

All of these measurements were standardized and adjusted for accuracy and precision when standards were determined, but the idea was that people didn’t need to have a set of calibrated instruments with accurate measurements marked on them in order to use them. Most people didn’t carry rulers and graduated cylinders around, and even though those things are widely available now, you still probably don’t carry them with you. They are in your house, in a drawer, waiting to be used only when certainty is required.

And even the conversions are meant to be functional without tools. When they standardized the length of a foot and an inch, it could have easily been adjusted to be 10 inches to a foot. 12 was used because it is easier to divide 12 without accurate markings. If you have a string that is 12 inches, fold it in half to get 6 inches, fold it again to get three inches. Or fold it in thirds (three equal lengths) and you have four inches. Fold that in half twice over again and you have an inch. Likewise, a gallon is 16 cups, because 16 can be divide in half 4 times to get a cup. Conversion by division means you don’t need to have as many different tools. A pound of sand and a balance can be used to find an ounce of sand without any additional tools, and you could probably get pretty close without the balance.

It is rarely important to be able to convert inches to miles. The ratio between them is arbitrary, because they are meant to measure vastly different things. Both are length, but an inch is the ground covered by a worm in a single contraction, and a mile is the ground covered by an army after a thousand paces. It’s dead simple to convert milimeters to kilometers, but how often do you actually need to do that accurately?

100 degree F is very hot outside. 0 degrees is very cold. Upper third is beach weather, be careful about overheating. Lower third, might snow, be careful about freezing to death. Water boils over a fire, and that’s about as accurate as you need to be most days. Modern digital tools and electronics have simplified all of these processes. The only time people actually need to use Imperial conversion rates is in school when you learn (and are tested on) how many feet are in a mile or how many BTUs it takes to raise the temperature of half a cup of water by 7 degrees. Of course that’s going to suck because it’s like mining for coal with a garden trowel. That’s not what it’s meant for. But you also wouldn’t use a backhoe to plant petunias, either.

I grew up using both Imperial and metric. Both have their uses, and both have pros and cons. Personally, I hate trying to describe the weather in Celsius. The differences between too hot and too cold are crammed between -20 to 40 degrees. What kind if scale is that? The difference between 38 and 43 is life threatening. Why should the boiling point of water be relevant to choosing between a sweater and a tee shirt? I don’t need to find the joules it will take to defrost 17 grams of ice on my car window. The benefits of the metric system are not relevant to my everyday existence, nor are the disadvantages of the Imperial system.