Comment Try DrawWell (Score 1) 80
DrawWell is a very affordable ($49) general drawing program for Mac OS X that has document scaling built in for exactly this sort of use. Just set a scale and your preferred working measurement units in the Document Inspector Measurements tab and off you go! You even get handy tool tips giving a shapes current dimensions next to the cursor while you are drawing. Couldn't be easier. See www.drawwell.com
