06 / 08
Convert hardness reported as mg/L CaCO3 to ppm, mmol/L, meq/L, German degrees, French degrees, and grains per US gallon.
FormulaAll outputs are converted from mg/L as CaCO₃
Calculated result
Result—Enter valid values
A
How the calculation works
Enter hardness on the calcium carbonate reporting basis. The converter applies fixed unit factors and also shows the U.S. Geological Survey descriptive hardness class.
B
Limits and responsible use
Hardness reported in another chemical basis must first be converted to CaCO3 equivalents. The descriptive class is a general USGS convention and is not a treatment specification or drinking-water safety determination.
Formula reference
The calculation and interpretation are presented with their assumptions so the result can be independently checked.
View U.S. Geological Survey: hardness of water ↗