30 is hot.
20 is nice.
10 is cool.
0 is ice.

40 and 50 can just not, please.

As a Norwegian:

• 100 is boiling
• 40 is we all gonna die
• 30 is hot
• 20 is a little warm
• 10 is a little cool
• 0 is cold
• -5 is maybe time for a jacket
• -10 shit, it's freezingly cold outside!
• -15 I'll stay indoors if I can

I regularly convert between the two just by remembering the conversions for 10, 20, 30, and 40. It's actually pretty easy.

• 0C is 32F (of course)
• 10C is 50F
• 20C is 68F (a cool room temp)
• 30C is 86F (reciprocal of 20)
• 40C is 104F

If you ever forget what one of them is, then just add 18F for every 10C from the last one you remember.

This is actually great, I've never found a good way to remember Celsius temperatures. I might go closer to Terrasque's scale though, 30 is definitely hot where I am.

Metric:

10 mm = 1cm, 100 cm = 1m, 1000 mm = 1m, 1000m = 1 km.

1 cm3 water = 1 gram

1 Watt heats 1 gram of water 1 C°

1 dm3 water = liter = 1 kg

1 m3 = 1000 kg = 1 tonne

Imperial:

1 mile = ?? yards = ?? feet = ?? inches

1 ton = ?? stone = ??punds = ?? oz = ?? grain

1 Galon = ?? pints = ?? fluid ounce

1 inch3 = ?? grain = ?? power to heat ?? fahrenheit

There is no system to any of these, they are unscientific and impractical.

How does Imperial still have any relevance as a measurement system?

O F is the freezing temperature of a saturated brine solution, while 100 F was the body temperature of a human. Yes, body temperature has been revised a bit, but the two points were chosen as stable points that anyone could access that would generally be unchanged by pressure changes, etc. Human homeostasis is quite good at keeping a temperature in a narrow range. Also, boiling is massively affected by air pressure. At 5000' elevation, boiling is approximately 202 F and continues to get lower as altitude increases. Lots of people live at higher altitudes. (Hi! I am one of them !)

Edit: I was a little off on the temperature selected for body temp, but still pretty close: https://en.m.wikipedia.org/wiki/Fahrenheit

It is convenient because they are used to it. That is all there is to it, and peace be to that.

It only becomes silly when they begin to claim that F is better for "human temperature", because again it all comes down to what you are used to and celsius is just as convenient if you are used to that.

Well, I'm..american, so I'm generally too broke to leave my house. I will openly admit I'm increasingly jealous of the French tendency to fuck shit up at the slightest inconvenience. They seem to know a lot more about getting things done.

I think one would also have to account for geography in that, no? If a country were landlocked and surrounded by a ton of others that all used the same separate system that they themselves do not, then there would be very significant reason and pressure to change. As much as it's derided for it, America IS very much a universe unto itself, and the only dealings it has with nations that do things differently are in areas of work that have switched over to more standard measurements.

All science and engineering are primarily or totally done in metric after we crashed the Mars Orbiter headlong into the dirt at mach speed. Everything else tends to use the more mathmatically sensible kelvin. Mexico uses metric and celsius, but I've literally never had a reason to go to mexico and probably never will. Canada uses both, but same deal.

I make a concerted effort to include both systems whenever I have to type for an audience of mixed/ambiguous nationality, but in my day-to-day, I will never meet another person who can easily switch between them and I have no use to do that either. It is a useless skill for me to have. Despite this, I have the sense that I see more europeans complaining about farenheit than I ever see Americans complain about celsius existing, and for such a damn stupid populace, I'm left to assume we either comment less or google it more.

Regarding projecting, I could be tongue-in-cheek and ask if you've ever met a European before. Our food. Our language. Our buildings, cities, cars, media, sports, slang, holidays, garbage disposals, windows, classrooms, whether or not we take our shoes off in the house. I struggle to think of a single subject you guys will not routinely make an inordinate amount of fuss over, as if it killed your children, and I'm convinced at this point that it's for love of spite and there's literally nothing we could do to make Europe happy if we wanted to. It makes sense that any chance to acknowledge the alternate measuring system would be prime ribs.

Brits especially will snark about american english that routinely turns out to be a defunct british word. Germans will complain about the drywall, but their own houses have the same drywall. Houses in Switzerland are made of wood, but nobody bitches at the Swiss.

Parting note, the downvote feels in keeping with that kind of pettiness.