Why does everyone forget the UK and Canada?
The numbers don’t work out too, “litres per 100km”. Why not millilitres per km (or litres per gigametre)
I drive X miles (or X km), I then fill up with Y litres (or Y gallons)
If I put 40 litres in my car and do 16 km per litre that’s 640km of range, simple calculation of 40x16
If I need to travel 260km at 20km/litre I need to but 260/20 litres or about 13 litres.
If I put 40 litres in my 3.6 litre per 100 km my range is 40/3.6 = 11 x 100 = 1100km.
If I need to do 260km at 3.6l/100km I need to do 260/100 = 2.6, times 3.6 = 9 litres.
With the “metric” way you need to do two calculations.
if you insist on using volume per length, I’d personally prefer 36ml/km, then I know I need 36x260 ml of fuel to go 260km, or my 40,000ml tank will take me 40000/36 = 1100km.
> I drive X miles (or X km), I then fill up with Y litres (or Y gallons)
This isn't what most use the liters per 100km for though. People just fill up whenever the light on the car tells them to. Mainly the number is used to compare cars when buying a new one. Some keep track of the actual consumption to notice if something is wrong with their car (just write down the current number on the odometer and how many liters you put in on some paper/app/whatever. you can do the actual calculations later)
At least this has been my experience here in Finland.
> With the “metric” way you need to do two calculations.
That's really an absurd way of looking at it, because one of those calculations is a division or multiplication by 100, and 100km happens to be a typical distance someone might be interested into finding fuel efficiency.
So the answer to me is an immediate mental computation, 2.6 x 5l = 13, you never ever need to compute consumption per km, express things in ml etc.
Your own "easy" examples look to me very intuitive and convoluted, so I guess the systems are 100% comparable, the only difference is the power of habit.
Measures are much more common in inches, foot and miles than metric. Volumes are much more common in cups, gallons, pints than metric. Weights are more common in pounds and ounces than metric.
That's in almost all domains, not just "a few high-profile holdouts" (even cooking, where it kills me that quantities of solids are in "cups" rather than grams...)
I think this is partially true, particularly with the older generation. People often talk about their height in feet and inches, and their weight in stone and pounds.
> Volumes are much more common in cups, gallons, pints than metric. Weights are more common in pounds and ounces than metric.
Your experience seems to be very different to mine. To be honest I have no idea what a gallon even is, and no intuitive concept of an ounce. The only place I have ever seen measurements in "cups" is one chicken biryani recipe I found on an American website. (I agree it's bizarre: half a cup of mint leaves - wtf?!). Any recipe published in the UK in the last couple of decades tends to be in grams and millilitres. Example picked at random: https://www.bbcgoodfood.com/recipes/chocolate-courgette-cake
I rarely see/hear/use imperial outside pints and road signs, or for “sizes” like screen or clothing waist sizes, unless I’m talking to people a generation older than me (I’m 40).
Every recipe site I use either has both or is entirely metric, and I only ever use metric. I’d probably look elsewhere if a search turned up a recipe in imperial only.
Even distances are in KM outside of driving (because of the road signs).
Pretty much everyone I know talks about their weight in KG. Heights do seem pretty split between cm and ft/inches but everyone understands both.
Most liquids except beer and cider (including other alcohol like wine and spirits) are in litres and ml.
It’s very obvious to me how metric-first life is for me because visiting America involves constant conversion and thinking whereas everything in other European countries (which are generally entirely metric) comes easily.
Ask an average American to give you the length of their car, size of their kitchen or weight of a brick in metric and they'll have no clue. The average British person can do this, because education has been metric for 50+ years and the least-technical industry (e.g. construction, DIY) is metric.
(See e.g. https://www.diy.com/, the largest consumer-facing DIY shop in Britain. It's 20kg of 10mm gravel, doors in millimetres, paint in litres. I can't even see a button offering an imperial conversion.)
The USA only uses metric in some important industries.
Britain uses it for lots of "unimportant" things, like construction/DIY, medicine, health care, cooking, sport/fitness.
We're still a bit of a mishmash, but it's not as bad as it might seem from outside.