Conversion Formulas

What is Alkalinity?

Alkalinity is defined as a measure of the buffering capacity of water to neutralize strong acid. This capacity is attributed to bases that are present in natural waters including OH-, HCO3-, and CO32-. More alkalinity in your water sample means more buffering capacity of your water sample.

In order to determine Alkalinity of your samples, samples will be titrated with sulfuric acid or hydrochloric acid to a certain pH end point (pH 8.3 for Phenolphthalein Alkalinity and pH 4.5 for Total Alkalinity), and the volume of the acid used for the titration will be recorded.

What is Total Alkalinity?

Total Alkalinity is the amount of acid used to reach pH 4.5. (ml) x 50,000 (mg CaCO3/eq) / sample volume (ml)

Here is an example on how to find Total Alkalinity: 18ml of 0.01M of Sulfuric Acid was required to Titrate 50ml of your sample to pH 4.5.

Total Alkalinity= 18(ml) x 0.02(eq/L) x 50,000 (mg CaCO3/eq) / 50(ml) = 360(mg/L)

Total Alkalinity Products

Water Hardness Levels

Soft: 0 to 75 mg/L as CaCO3

Moderate: 76 to 150 mg/L as CaCO3

Hard: 151 to 300mg/L as CaCO3

Very Hard: Above 301 mg/L as CaCO3

Total Hardness = Calcium Hardness + Magnesium Hardness

Water should have a total hardness of less than 75 to 85mg/l as CaCO3 and a magnesium hardness of less than 40mg/l as CaCO3 to minimize scaling at elevated temperatures.

Total Hardness Strips

What’s the formula to convert mg/L to ppm?

1 mg/L = 1 ppm for dilute aqueous solutions. For example, a chlorine concentration of 1.8 mg/L chlorine is equivalent to 1.8 ppm chlorine.

How can I convert percent transmittance to absorbance, or absorbance to percent transmittance?

To convert a value from percent transmittance (%T) to absorbance, use the following equation:

  • Absorbance = 2 – log(%T)
  • Example: convert 56%T to absorbance:
  • 2 – log(56) = 0.252 absorbance units

To convert a value from absorbance to percent transmittance, use the following equation:

  • %T = antilog (2 – absorbance)
  • Example: convert an absorbance of 0.505 to %T:
  • antilog (2 – 0.505) = 31.3 %T
What is a grain per gallon (gpg)?

One grain is equivalent to 64.799 milligrams. It’s a historic unit of weight once used for barleycorn. A grain per gallon is the weight of a substance in one gallon of water, similar to a milligram per liter.

What’s the formula for converting grains per gallon (gpg) to milligrams per liter (mg/L)?

Multiply gpg by 17.1 to get mg/L (1 gpg = 17.1 mg/L). For example, a hardness test result of 3 gpg as CaCO3 is equivalent to 51 mg/L as CaCO3. What’s the formula for converting grains per gallon to milligrams per liter? 1 grain = 64.799 milligrams 1 gallon = 3.785 liters 64.799 divided by 3.785 liters = 17.1 1 gpg = 17.1 mg/L

Brew Kits

What's the formula for converting calcium carbonate ppm (as CaCO3) to ppm Calcium (ion)?

Multiply ppm (as CaCO3) by 0.4


Converting calcium carbonate ppm (as CaCO3) to Degrees of General Hardness (dGH)

Simply multiply ppm (as CaCO3) by 0.056


How do I convert sodium chloride ppm (as NaCl) to chloride (as Cl-1)?

You would multiply ppm (as NaCl) by 0.6097


What's the formula for converting chlorine dioxide ppm (as ClO2) to chlorine (as Cl2)?

Multiply ppm (as ClO2) by 0.5255 to get your answer


How do I convert chlorine ppm (as Cl2) to mono chloramines ppm?

Multiply ppm (as Cl2) by 0.7259 to get your answer

Chlorine Dioxide

What's the formula for converting hexavalent chromium ppm (as Cr+6) to sodium chromate ppm (as Na2CrO4)?

You need to multiply ppm (as Cr+6) by 3.115


Converting hexavalent chromium ppm (asCr+6) to chromate ppm (as CrO4):

You will multiply ppm (as Cr+6) by 2.231


How do I convert calcium carbonate ppm (as CaCO3) to magnesium ion (as Mg+2)?

Multiply ppm (as CaCO3) by 0.2439


What is the formula for converting calcium carbonate ppm (as CaCO3) to magnesium chloride (as MgCl2)?

Multiply ppm (as CaCo3) by 0.956

Magnesium Products

What is the formula for converting manganese ppm (as Mn+2) to potassium permanganate (as KMn04)?

Multiply ppm (as Mn+2) by 2.876


What is the formula for converting manganese ppm (as Mn+2) to potassium permanganate (as MnO4-)?

Multiply ppm (as Mn+2) by 2.165

Manganese Products

Why is it important to test for Manganese?
Long term exposure to manganese can cause toxicity to the nervous system and Parkinson’s like symptoms – particularly in children, the elderly, and pregnant mothers. So, it is very important to test for high levels.

One of our favorite websites, Wolfram Alpha does online dynamic computations based on a vast collection of built-in data, algorithms, and methods.



Snoeyink V. and Jenkins. D. 1980. Water Chemistry. JOHN WILEY & SONS, New York. ISBN 0-471-05196-9