I do my own calcs also, using a spreadsheet I built. It calculates gravity, bitterness, color, mash volumes, mash temperatures, and yeast starter growth.
I used to use Beersmith and found it to be pretty helpful. But I wanted to make my own to better understand what the calculators were doing, and also so I could customize it as necessary.
I use EZ Water 2.0 for mineral additions.