I don't know if anyone will find this useful or not, but I thought I'd share it anyways. I threw together an excel file with a form that helps you enter all of your water parameters, and then calculates your CO2 levels for you.
I also included instructions for API tests in there for quick easy reference.
You will need to save the file to your computer first, for some reason it doesnt work right if you open it directly from the web.
Anyways, here it is...