I generally formulate my recipes on BrewR (android) and I've worked out my volumes from experience. Never had a problem so far. I don't think I need to be so accurate at the scales I'm doing and I've been more than happy with results so far.
As long as I can work my IBU, efficiency, colour (through BrewR) and I know I'm going to be left with 23 litres of wort at the end, I'm happy.