If you're used to metric, are you pretty much expected to be able to convert/multiply quantities in your head, since it's mostly by factors of 10?
This part of the OP, is a typical question from a person who is used to imperical.
Even though you do know it, there is still the problem of really understanding that unlike in the imperical system there are no conversion in metric. That is the reason why I always say that metric is objectively easier then imperical.
to measure distance/length
you use: inch, feet, yard, mile (conversions necessary)
we use: meter (no conversions)
to measure volume
you use: cup, ounce, gallon
we use: liter
you use: cubic inch / cubic feet (I have seen thes being used)
we use: m3
to measure weight
you use: grain, ounce, pound, stone
we use: gram (1000 gram is 1 lieter of water)
As you can see, not only does the metric use one unit per variable, the different units for the variables are also clearly related to eachother.
The only thing you need to know is that
milli = 1/1000
centi = 1/100
deci = 1/10
deca = 10
hecto = 100
kilo = 1000
I grudgingly admit that metric is better for scientific purposes (I'm a chemist, so I pretty much have to ), but I really think Imperial is better for real life. It's hard to cut things into 10 pieces, but pretty easy to eyeball 1/3s and halves, and by extension 1/12ths and 16ths. And temperatures: 0C is the feezing point of water, but only if it's pure and at sea level. 0F, OTOH, tells you something no matter where you live: it's COLD. And above 100F, yeah, it's HOT.
I have to say though, my absolute favorite unit is the stone. 14 lbs. Really? It seems so delightfully random. I really want a scale to measure my weight in stones.
Actually, the point of metric is that you can easily cut things into anything, there is no reason to limit yourself to tenths only.
1/3, 1/2, 18/ etc work just as well in metric as in imperial.
I find it odd that you believe that it is easier to need to converse variables in real life, instead of not having to do any conversions, within one variable