This could be another poll for Kai. He loves polls.
What brewing software do you use? Promash, beersmith, strangetools, pen and paper, your own software.
Make sure, when you are working out your calculations by pen and paper, say you are after 23 litres into the fermenter, you loose 1.5 litres of wort to trub and hops and some in the pipelines, that you are actually brewing 25 litres and should bitter accordingly. Brewing software makes this easy when you set up your brewhouse parameters.