Conversions From standard to metric units

I am starting to use R for almost any sort of calculation that I need.
 I am a biologist that works in the states, and there is often a need
to convert from standard units to metric units.  Is there a package in
R for this already?  If not I believe that I am going to write some of
the most often used in function form.  My question is should I include
this in my StreamMetabolism package.  It is not along the same theme
lines, but could loosely fit.  The reason that I ask is that I don't
want to clutter CRAN with a small package containing some conversion
functions because I am to lazy to source them into R every time that I
use them, but I also don't want the StreamMetabolism package to turn
into StephenMisc Fuctions.  Thoughts, comments, or suggestions would
be appreciated.