Manfred · the unit translator
Hardness converter
Translate between the units every test kit invented its own version of. dKH, ppm CaCO₃, meq/L for carbonate hardness; dGH and the Ca/Mg split for general hardness.
Carbonate hardness
Enter a KH value to see the equivalent ppm and meq/L.
General hardness
Enter a GH value to see the equivalent ppm and Ca/Mg breakdown.
The numbers behind the conversion
Both °dKH and °dGH express hardness as calcium-carbonate equivalents in German degrees. One German degree of hardness corresponds to 17.86 mg/L of CaCO₃ — that's the conversion factor every unit on this page hinges on.
1 °dH = 17.86 ppm CaCO₃ = 0.357 meq/LThe Ca/Mg breakdown assumes the hardness splits 4:1 between calcium and magnesium (about 6.6:1 by mass), which is typical of unmodified tap water from chalk aquifers. If you remineralise RO water with a known Ca:Mg blend, recalculate Ca and Mg from your remineraliser's spec sheet instead of from this page.
In the app, Stormy charts your KH and GH in German degrees over time, so you see the drift between water changes.