Water Hardness Calculator
Convert your reading between all units in seconds — °dH, °e, ppm CaCO₃, grains per gallon, mmol/l and mval/l. Also for carbonate hardness, phosphate, sulfite, nitrate, ammonium and conductivity.
Results without warranty · The scale follows the common mg/L CaCO₃ classification (for orientation).
Total hardness
The sum of calcium and magnesium ions — the key value against limescale.
- Definition
- Total hardness is the sum of the dissolved calcium and magnesium ions. It is stated in °dH, ppm CaCO₃ (mg/L) or grains per gallon (gpg): 1 °dH = 17.8 ppm CaCO₃ = 1.04 gpg.
- Why it matters
- Hardness is the key value for scale protection: on heating, calcium carbonate precipitates as limescale in boilers, heat exchangers, tanks and pipes, lowering efficiency and raising energy and maintenance costs.
- Where measured
- At the inlet (raw-water hardness), downstream of the softener (residual-hardness check) and continuously in boiler and cooling water.
- Typical values
- Tap water ranges roughly 60–400 ppm CaCO₃ (soft to very hard). Softened boiler feed water should reach a residual hardness near 0.
- Measurement
- Drop-by-drop titration, pass/fail limit test or continuous online analysis (SYCON / LIMES).
- Good to know
- Carbonate hardness is the part of total hardness that precipitates on heating — both values are usually considered together.
The RLS Wacon water hardness calculator
This tool converts your reading between all common units in seconds — for total and carbonate hardness plus the boiler-water parameters phosphate, sulfite, nitrate, ammonium and conductivity. Choose a parameter, enter your value and unit, and you instantly get every unit, the hardness category and the right measurement method and products.
Units & conversion
Rule of thumb: 1 °dH = 17.8 ppm CaCO₃ = 1.04 gpg = 1.78 °f = 1.25 °e = 0.178 mmol/l. Reconcile manufacturer, lab and water-utility figures on a single scale.