I agree with Allen that it really does matter much to bees whether it is by
weight or volume...

I've mixed many 44 gallon drums of syrup by filling to the first 1/3
reinforcing ridge with cold water, then dumping in enough sugar to fill to
just about the second ridge (ie, 1:1 by volume), then stirring over a period
of time until it all dissolves.  And if it doesn't, throw in another bucket
of water!

For the calculationally inclined, you can play with a Javascript calculator
at http://www.beekeeping.co.nz/info/convert.htm#sugarmix2 to see the
different effects...