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.
Manfred · the unit translator
Test kits report whatever unit their country settled on — German degrees, ppm, milliequivalents. Manfred translates between them so the number on your bottle matches the number on the page.
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 a 4:1 mass ratio, 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 converts these for you on every test entry, so the chart never asks which unit you typed.