> is it really so hard to have a ruler with both measurements? I have a ruler that lets you convert from font point to two other measurement units to inches, for page layout.

The problem with the imperial unit system rather is that it does not form something "to build more complicated units out of".

For example: if you want inch (in) as a unit, why not have "in^2" as a corresponding small area unit and "in^3" as corresponding volume unit?

Additionally, there should be constant/regular conversion factors between the various subunits of a measure, i.e.

  10^-3 km = 1 m = 10 dm = 100 cm = 1000 mm = 10^6 µm = 10^9 nm = ...

  1 lea = 3 mi = 24 fur = 240 ch = 5280 yd = 15840 ft = ...