You have to do it multiple times since there is more than one value. Also include time for switching tabs etc, and then returning and working out where you were.

FWIW if you're on a Mac, Spotlight will do simple unit conversions, so you can just cmd-space and do it in the popup without having to leave the page.

That said yeah US units are absolutely brain-dead and confusing, how hard is it to put real units in parenthesis?

Multiply this by every single person who has to do this whole process.