Alkalinity and Hardness scales

Hardness unit conversion

 
mmol/L
ppm, mg/L
dGH, °dH
German
gpg
°e, °Clark
English
°f
French
mmol/L

1

0.009991

0.1783

0.171

0.1424

0.09991

ppm, mg/L

100.1

1

17.85

17.12

14.25

10

dGH, °dH

5.608

0.05603

1

0.9591

0.7986

0.5603

gpg

5.847

0.05842

1.043

1

0.8327

0.5842

°e, °Clark

7.022

0.07016

1.252

1.201

1

0.7016

°f

10.01

0.1

1.785

1.712

1.425

1

For example: 1 mmol/L = 100.1 ppm and 1 ppm = 0.056 dGH.
  • Parts per million (ppm) is usually defined as 1 mg/L CaCO3 (the definition used below). It is equivalent tomg/L without chemical compound specified, and to American degree.
  • Grains per Gallon (gpg) is defined as 1 grain (64.8 mg) of calcium carbonate per U.S. gallon (3.79 litres), or 17.118 ppm.
  • mmol/L is equivalent to 100.09 mg/L CaCO3 or 40.08 mg/L Ca2+.
  • degree of General Hardness (dGH or German degree (°dH, deutsche Härte) is defined as 10 mg/L CaO or 17.848 ppm.
  • Clark degree (°Clark) or English degrees (°e or e) is defined as one grain (64.8 mg) of CaCO3 per Imperial gallon (4.55 litres) of water, equivalent to 14.254 ppm.
  • French degree (°F or f) is defined as 10 mg/L CaCO3, equivalent to 10 ppm. The lowercase f is often used to prevent confusion with degrees Fahrenheit

 

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