I usually go with 240 ml if scaling down and there are fractions involved for slightly cleaner numbers.

Another "close enough" value is the binary inch of 25.6 mm. Makes dealing with /32s and /64s oh so much easier.

True. At that point you're close to the intent of teaspoons/tablespoons/cups with easier to remember units. tsp = 5ml tblsp = 15ml cup = 240ml

with all the handy halvings in between + higher granularity of ml.. 'course I'm usually approximating on a gramme scale anyway.

But for larger stuff I round up to 250.

Speaking of feet - I got irritated when buying shoes and trying to convert shoes sizes.

It turns out that UK/US sizes are based on the length of a barley corn.

Quite why it isn’t just in centimetres is baffling. https://en.wikipedia.org/wiki/Shoe_size

I'll give you this one, but only with the qualification that inches would be fine too. There's no benefit to the manufacturers in more rational standardization, though. As with women's clothing sizes, why would Levi's (for example) make it easier for me to find something that matches my style and budget, from anyone other than them? Hell, even men's sizes which nominally are in inches do this! I have to go a size up in Levi's vs Wranglers because Levi's size small, the bastards, while Lee mostly run true to size but none of their cuts is really worth wearing. And don't even talk to me about boot sizes!

Inches vs. centimeters? Baby stuff. Get on my level. :D

And now the famous triviality of order-of-magnitude and unit conversion goes entirely out the window...

That’s where duodecimal comes in…

Duodecimal metric! Tell me more.

You do what you can with the limitations of the system. Some rounding helps with a lot of feet/cups. 4 metric cups to the litre..