If someone gives directions in miles in Hawaii, they’re usually military. Makes sense since 30 minutes to get from A to B is meaningless if you’re walking on foot versus driving there. However, mainland visitors tend to ask for distance in miles, to which we answer “Umm…don’t know how may miles, but it’s a 20 minute drive!”. Works well when a “Around the Island trip” around Oahu takes less than 2 hours during non-traffic hours. During traffic hours or if there’s an accident, you may as well sleep in your car! 
I’ve been metric for most of my life, but still cannot get my head around cm to measure vertical heights.
When you hear police reports (for example) of a suspect being wanted for questioning over some crime, and they say, “…dark hair, Caucasian, 180cm tall…” I have NO CLUE what that is. I just cannot visualise it.
But tell me the person is 5’ 8" or 6’ 3" and I’m fine and dandy.
Depends on the distance, in my experience.
Europeans sometimes try to do the opposite. .380 ACP is sometimes 9x17mm or 9mm Kurz (short).
The French considered that, and actually implemented a decimalized calendar, but chopping heads and/or dictatoring got in the way.
Decaminutes or hectominutes, maybe? A centiminute would be 1/100 of a minute.
Decimeters is really the best (metric) scale for human heights (if you’re over the age of about 2 anyway). No-one can really tell the difference between a 180 cm and 181 cm person, but 17 vs 18 decimeters is easy to spot
(now I’m trying to remember if I’ve even heard a decimeter used in the wild since my high school science teacher teaching us what a liter is. Coming up blank…)
I’m American & I use the metric system.
I no longer even think in Fahrenheit at all. I also stopped doing the actual conversion and do a rough conversion if people ask. If no one asks, I don’t bother.
I still use miles when I’m talking to most people, but I think in meters and kilometers and do the conversion in my head. And I find I’m less willing to do that as the years pile up on me.
:smack: Yes, you’re right.
As a scientist, I use metric all the time at work. Occasionally I’ll convert report a distance in miles if the general public is the target audience for the sake of comprehension.
So if you used metric around me, I probably wouldn’t notice. But I think it just makes good sense to speak in the way that will help you be understood.
We have measuring scales to quantify real things. It’s absolutely required that the reference points are distinct (some physical constant). It helps if the constant is universal (a wavelength of light is good). It is better if the constant is accessible (I can’t generate a specific wavelength of light, but I can definitely freeze water). It is best if the constant is relevant (I cook when I boil water. I avoid roads when water freezes). And it helps most if the system is mathematically easy to work with (metric is powers of 10, vs powers of 2 times 3 which somehow add up to a mile of 5,280 feet).
The metric system strives to provide all of these. That’s why most of the world has adopted it. The imperial people is stupid and is only followed by countries that want to demonstrate they’re so powerful they don’t need to be smart.
Blasphemer! Commie! J/K!
Edit: Oh wait…your nick points to you probably not being American. Carry On! 
That’s the wrong question, though. A better question is “why do I need a measuring scale that changes my familiar 86 degrees into the confusing and vaguely communist 30”. The answer is that because 30 is the answer produced by a better scale, which itself is produced by a better system. That system is better partly because it makes it easier for all of to calculate measurements in our heads, but (IMO) because it eases the job of engineers and scientists who make things that help make our lives easier and more interesting.
How hard is it to adopt this? Take a good look at your own temperature scale. It probably breaks down
0. damn cold (below 0C)
- water freezes (0C)
- i’m chilly (10C)
- i’m cool (15C)
- i’m fine (20C)
- i’m warm (25C)
- i’m hot (30C)
- really hot (35C)
- hell with this, I’m visiting my mother in Minneapolis (40C)
- hottest desert hot (45C)
Nice round numbers in Celsius, but all kind of weird random numbers in Fahrenheit. The point is not that round numbers are better, the point is that if we’re talking about everyday familiarity, you’re only talking about 10 temperatures, so fewer degrees is better. Actually I’d like to see the above scale reduced to just 10 degrees, but scientific calculations also use basic relationships like 1 degree per 1 gram equals 1 of some other measurement, so it would mess that up.
The OP should always use at least three decimal points AND use the word “approximately”:
“The distance to St. Louis is approximately 174.683 kilometers.”
Not I. The broadest span in which my subjective experience differs is 5F rather than 5C, and it’s often tighter than that. Sometimes I feel fine just 2 degrees F hotter or colder. Granted, that is more than 1C, but it’s debatable whether units should be slightly finer than, or exactly equal to, the smallest appreciable difference. I’m in the same boat with regards to cm versus inches to measure height, since the inch is the smallest appreciable difference in height to me but I could see someone wanting a slightly finer scale; except that in the foot versus the meter, the foot wins easily with regards to height because people rarely deviate from “1-meter-something”.
I was speaking more toward our everyday habituations of “what is hot weather? What is cold weather?” But if you want to speak to finer degrees of comfort, amazingly enough, Celsius has you covered. 1 degree C is equal to 1.8 degree F. I hope you aren’t going protest that you can really detect a difference of 0.2F.
Honestly I can’t detect any coherent reasoning here except an appeal to habituation.
I can say the foot doesn’t win any contest except which measurement you learned earliest. If precision like ‘foot’ meant anything, Americans would also insist on saying “9 furlongs away” because “about a mile” isn’t quite precise enough.
Of course if you dispute that reasoning, consider the appeal to popularity: there’s also the fact that most of the world has zero problems saying 1.75 meters tall instead of 5’9". It’s actually more precise than what you’re accustomed to.
Height was one of the last holdouts in Aus after forced conversion. That and bookshelves. Eventually everybody who knows their height in feed and inches dies out. And everybody who reads books.
But boiling water is “Put water on stove, wait for it to boil” and roads don’t freeze at 32F or 0C because the road absorbs heat, cars drive over it, it gets salted, etc. So in neither case is there a “relevant constant”.
Outside of scientific applications, there’s probably very rarely a “relevant constant” (whether you’re baking at 350 or 352 isn’t going to matter; check your brownies to see how they’re looking) and no one is arguing against Celsius for scientific applications.
The math is easier with metric. Talking to most people on the planet is easier with metric.
Pretty much everywhere I’ve been in the US, transit distances are given in units of time. It doesn’t matter what the mode of transit is, either. Driving, walking, taking the train, canoeing, whatever–how long it takes to get from Point A to Point B is what counts.
By the numbers, I’d be best off speaking Mandarin when talking to a resident of planet Earth but it almost never really works out that way.
How many people speak Mandarin? About 900 million out of about 7.35 billion people.
How many people use metric? About 7 billion out of 7.35 billion people.
Choose your battles.