GH and KH

Definition

GH (general hardness) is calcium plus magnesium. KH (carbonate hardness) is alkalinity, mostly bicarbonate. Coffee recipes target roughly 50–80 ppm GH and 40 ppm KH as CaCO₃, in the SCA ballpark. High KH mutes acidity; very soft water can taste sharp and scale less. German degrees: °dH ≈ ppm / 17.8. Test strips and lab reports disagree — treat recipes as starting water, then taste.

Calculators that use this

• Water chemistry

  Barista Water Recipe Calculator

  Build brewing water from target GH and KH as ppm CaCO₃. Get Epsom salt and baking soda in milligrams and grams for a chosen volume.

• Water chemistry

  Water Hardness & Alkalinity Calculator

  Convert GH and KH from ppm as CaCO₃ into German degrees and their ratio. Useful when a test kit and a coffee recipe disagree on units.