> buy a pint of beer,

This is not really a problem I think. It's become an object in itself and you don't really use this as a reference when buying milk or water I imagine. In France you can also get a "pinte" of beer (pronounced as "paint"), it's probably a relic from before the metric system and probably not the same as the English pint though.

Celsius vs Fahrenheit is tricky because Fahrenheit does have some nice properties and several sciences use Kelvin anyway. I think the best one would be a new one, rescaled to match with 0°C and 100°F.

Calculating mpg is an interesting one because even if you moved to calculating km per liters it would still doesn't match the most common usage, we use liters per 100 km.

One thing where almost everyone fails in my opinion is shoe sizes. Why can't we just use centimeters? Instead we have four competing standards and the EU one doesn't relate to anything.

In France you can also buy vegetables by the pound (une livre), but if course both of these are just shorthands for half a litre and half a kilo, respectively, they're not actually the old measures.

I was surprised, when I found out, how comparable many of those relics are. Many countries had a variation on a pint, a pound etc, that were in the same ballpark but never quite the same. I'd always presumed pre-metric Europe would have much wider variation in units. Maybe they stem back to the Romans, like £sd did.

You'd be surprised on milk - I'd say the commonest supermarket sizes are still really pints. Usually 2.272l (4.0 pints), and 2 and 6 pint equivalents. Posh variants like some organic, filtered etc are in 2.0 litre packs - mostly opaque so you don't notice the 4 pint capable pack with lower fill level. :)

Shoe sizes are infuriating. Would be nice to find a way to standardise, and have manufacturers agree on what size x means, as they've diverged wildly from reality.

> Fahrenheit does have some nice properties

Which exactly? Walter melting at 0°C and boiling at 100°C seems the most practical.

The main niceties are the increased granularity (nobody would use half °C in practice) and 100°F being the normal body temperature and a good landmark to relate to hot weather.

0°C is absolutely super practical and is imperative to have as a landmark. 100°C boiling water... it isn't really that practical in day to day use in my opinion (when was the last time you saw 100°C written on a device?). In the high temperatures the ones I care about in a practical sense are on the oven for cooking and on my soldering station, both much higher than 100°C anyway. The only time I care about boiling water temperature is when I am boiling water in which case I don't need a thermometer.

So I think 100°F is more interesting as a landmark than 100°C for intuiting temperatures. You can think of it as the percentage of how hot it is. But 0°C is more interesting than 0°F.

I don't understand why we want round numbers here. I know 40 C is "very hot" and for Americans that's 100 F. Using a rounder number makes absolutely no difference, since I'm never going to divide temperatures.

It doesn't even matter much for meters and kilometers, since I very rarely need to talk about things that are kilometers away and meters away in the same context. It's handy to have sane units for those, though, since there you can multiply and divide in your calculations.

Temperature arguments never seemed particularly compelling to me. They assume 100 is more convenient, which I find wrong, since you're usually talking about 102, 86, 95, etc anyway.

> increased granularity (nobody would use half °C in practice)

We use 0.1°C for even better granularity. E.g. weather sites, all my digital thermometers, etc.

> when was the last time you saw 100°C written on a device?

Daily. Ovens in Europe typically will have a temperature range that's something like 50-400 C. I've never seen oven without a 100 C setting. Sauna thermometers will typically go from ~20 degrees to either 120 or 140 Celsius.

> The main niceties are the increased granularity (nobody would use half °C in practice)

One decimal place is commonly used.

I don't live in the UK but nearby in Europe. I know a handful of Brits but have never heard them express temperatures in Fahrenheit (and they know I'm American, so if they switched I always figured it would be for my benefit). Is that really true about the hot weather thing?

Just this past week for example, my colleagues were complaining about the 33 degree heat wave, were excited for the weather to drop back down to the 20s on Friday, and were complaining about the random 31 degree heat wave coming on Saturday.

The only times I've heard reference to Fahrenheit in the UK is my grandma in the 1990s, and in tabloid newspapers when the temperature reaches 100°F.

These are the same tabloids that will do anything anti-European they can think of. I don't think it matters that people don't really know what 100°F is.

> but when it's hot, people always remember Fahrenheit and it's 80s, 90s, etc

The US is the only country using Fahrenheit as far as I know, I never heard anyone in the UK using anything other than Celsius. You don't even say "Celsius", just "degree", it's implied it's Celsius.

The tabloids still seem to like Fahrenheit for heatwaves, and I've heard it used reasonably often in summer - in offices etc. I can only remember hearing someone use deg F when it's 70+. It's certainly declining and not as common as say 30 years ago, but it's definitely one of the holdouts.

No one ever adds C or F, or even degrees very often, unless writing. It's -5; it's 30; it's 92, which are all self defining in UK climate.

Ah interesting, I checked and indeed the tabloids seems to keep Fahrenheit for some reason. I've never heard Fahrenheit spoken though.

I have the same experience. I'm an American expat so sometimes people will explicitly call out celsius for my benefit or as a joke, but yeah, nobody ever says celsius when they talk about the temperature here.

"What's the temperature?"

"It's gonna be 21."

"Got it, thanks."

That's how it usually goes.

You're not wrong, another example you missed is UK-people will give their weight in "stones".

I moved to Finland and I'm still not used to the idea of giving my height in cm/m, or weight in kg. Until now I've never needed to know either.

I've personally never heard anyone talk about temperature in farenheit

Interesting. At least Britain pushed for it for real and as you say, even with that it takes a long time. In US it's very lax. Government basically gave up finishing the job, so it's stalled.

There's other silly ones. Wood has been metric almost as long as I can remember, but 50x25mm is still commonly referred to as 2x1 etc. If it's PAR it'll be smaller than either. :) plumbing pipes and fittings are still mostly really BSP - British Standard Pipe uses inside diameter, metric outside. 15mm pipe and fitting is really a 1/2" BSP with imperial thread.

UK was probably too lax about it to be honest. They didn't require all packaging to use metric only until the last 20 years, so plenty of shops kept on putting up signs in pounds even if the till worked the price in kilos.

Since metric packaging was required there's been one clear downside - you're far, far more likely to have manufacturers hide price rises by dropping 5 or 10 ml or grams from a product, in an apparently identical pack. Repeat a few times and much is now randomly sized, where once all brands had comparable sizes. Choc bars, jam, used to be 1lb, 1/2, 1/4. Now some random number of g.