So, looking for my local water analysis online and found it.
It lists "total hardness" as 20, as measured using German Degrees of Hardness.
I then found this calculator for converting that:
Cactus2000: Converter for hardness of water
And it says that I'd have 142.94 mg Ca2+/l.
Lists all sorts of other stuff as well.
Firstly, I thought maybe someone would have a use for the calculator. Secondly, I cannot quite wrap my head around this. Is this an accurate way of generating my Calcium number? The water analysis doesn't list just Calcium on it. Thoughts?