I've used randys 2 part for a while now and it works great for me and is ridiculously cheap compared to the store bought 2 parts. And for what I spent on one bottle of Kent Magnesium, You can basically buy a lifetime supply by buying one bag of MAG flakes! Things cost enough in this hobby!!
The calculator is a great tool, its one of those things I wish I knew of when I first started!
Rick