@Tally-ho. Nice picture. I have been raised a science-type all my life. Math, chem, physics.
And yet, as I am lookin at your (clarifying) picture, I get the strange urge to say.

US: 1 mile = 8 furlongs = 80 chains = 1,760 yard = 5,280 feet = 63,360 inch. That is adventure.
SI: 1 km = 1,000 m = 1,000,000 mm = 1,000,000,000 µm. Admitting it is much easier, but also a bit boring.

Old habits die hard, there are still Dutch (wo)men who use “pond” and “ons” (0,500 kilo resp. 0,100 kilo).