That said, I think the US car industry has moved to metric and it is great to not need multiple sets of everything.
If we have 2mm of rain in Copenhagen this afternoon, and my yard measures 8m×12m, how much water must drain away?
2mm × 8000mm × 12000mm = 192 000 000mm³
= 192 000cm³
= 192 dm³ = 192 L
= 0.192 m³
2mm × 180km² = 0.002 m × 180 000 000 m²
= 360 000 m³
approx. = 360 000 tonnes.What about if it isn't water you are calculating but some other substance? You use a look up table to find the factors - we need to look up a but more in the table, but it isn't a big deal.
I always hear that argument about "but when will I need it?" If you're using this system then you're always going to use it. It comes up all the time, it's natural so you don't think about it too much.
Does it mean it's better? Well yes, but it doesn't mean other measuring systems aren't good. You don't need it, but you'll want it once you learn it.
The second is obviously relevant for the people responsible for rivers, storm drains, sewers, dams, hydropower and so on. When we start terraforming Venus, we'll need to add the conversion factor for sulphuric acid rain.
> my yard measures 8m
You use a very long unit of measure.
Sure I can do the math to calculate it in my head and take a few seconds.
How many meters are in 240cm? Don't need to 'calculate' it the same method. I just move the decimal over. 2.4m...
I say this as an American who finds our use of Imperial pointless. Infact, there is a highway in Arizona that uses metric instead of imperial, as it was a part of our move to metric. (The current measuring and weights system in the United States is based on Metric, we do use it, just converted into another measure)
Every time I need to add or subtract two measurements.
Quick:
What is 2' 3 5/8" plus or minus 1' 2 19/32"?
or
What is 701.7 mm plus or minus 370.7 mm?
Seriously I work with both everyday, and while I grew up with inches & feet and I still intuitively know how deep two feet of snow is better than 61 cm of snow, I'm really starting to hate the US measurements, and use metric whenever I can.
Also, whenever we deal with things from the rest of the world, it becomes a mashup of US and metric measurements.
The US almost converted to metric in the 1970s, but Nixon squashed it, basically on the complaints of what are surely the ancestors of modern US right wing know-nothings who didn't like "foreign" stuff.
Looking at it historically, the fractions made a lot of sense when things were more coarse, and the ability to split things into even sections, 1/2, 1/3, 1/4... was more common.
OTOH, Metric was designed for doing calculations - we already use the decimal system for all other math, so we should design a measuring system to use the same calculation system. It really does work better.
A few brake lines and some old exhaust bits might be SAE, but by and large vehicles are done with metric.
Personally I like that SAE has fewer sizes... Its frustrating as hell working on cars with a mixmatch of 6mm 7mm and 8mm bolts. oh this is a 15 but a few awkward 16s! Mostly though, cars are pretty standard. European cars seem to be basically - 7mm 8mm (hose clamps and other tiny stuff) 10mm (air filter housings and such where 8mm is to small) 12mm 13mm (misc bolts, intake manifolds, exhaust, almost everything) 15mm 17mm 19mm (these larger ones are basically suspension and other large components)