ppm in Solution Calculator

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Dilution Rate at mL/L

Dilution Rate at mL per US gallon

Concentrate Listed as

Check one box
%w/w >>> SG

If the concentrate is listed as %w/w
enter the specific gravity (SG) of the product
here (see explanation of SG below)

Element (symbol) Guaranteed Analysis ppm
Nitrogen (N) % as Nitrate (NO3 N)
Nitrogen (N) % as Ammonium (NH4 N)
Nitrogen (N) % As Urea CO(NH2)2
Nitrogen Total (N)
Phosphorus (P) % as Elemental P
Potassium (K) % as Elemental K
Magnesium (Mg) %
Sulfur (S) %
Calcium (Ca) %
Iron (Fe) %
Boron (B) %
Manganese (Mn) %
Zinc (Zn) %
Molybdemun (Mo) %
Sodium (Na) %
Copper (Cu) %
Chlorine Cl %
Cobalt Co %
Sillicon (Si) %
Selenium (Se) %
Nickel (Ni) %
Other %
  Total ppm =   
[ Print Data ]          

Definitions of Terminology

“Elemental” refers to a pure chemical element.

It is important to note that NPK (nitrogen, phosphorous and potassium) ratios on blended fertilizers do not always reflect the actual amounts of elemental phosphorous and potassium contained within a fertilizer.

Some countries (e.g. America) list P (phosphorous) as P2O5 and K (potassium) as K2O.

It is important to note that that phosphorous as P2O5 is only 43.641% elemental phosphorous and potassium as K2O is only 83.014% elemental potassium.

Therefore, when this system is in use a 20-20-20 NPK listed fertilizer truly reflects NPK 20-8.72-16.6 elemental NPK.

However, in some countries they list P and K as actual elemental P and K. This means that in some countries NPK ratios will reflect actual elemental NPK ratios while in other countries the P and K numbers will appear much higher.

It’s a crazy situation but one that you need to be aware of (just to confuse the situation further all other elements under the P as P2O5 and K as K2O listing standards are listed as elemental).

Where a product is listed as P as P2O5 and K as K2O convert these to elemental values before entering the elemental values in the P and K % fields of the ‘ppm in Solution Calculator’.

You will find a calculator on this page which does this for you (under ‘Conversion Calculators’).

Conversion Calculators

Convert phosphorous as P2O5 to elemental P
% P2O5 = elemental P %

Convert potassium as K2O to elemental K
% K2O = elemental K %


When potassium (K) is listed as K2O this represents 83.014% elemental K

When phosphorous is listed as P2O5 this represents 43.641% elemental P

In some countries (e.g. America) they list potassium as K2O and phosphorous as P2O5 while in other countries they list elemental values

For this reason we have included a conversion calculator

Convert ppm to %
ppm = %

Convert % to ppm
% = ppm


Microelements may be listed as ppm. Use this calculator to convert to %. Cut and paste the data into the ‘ppm in Solution Calculator’.

Establishing SG (Specific Gravity) for %w/w Listed Products

SG stands for Specific Gravity. Some use the term density but density can also refer to solids. Specific Gravity refers to the weight/volume of liquids in relation to water, usually measured in g/mL or grams per Millilitre. So one ml of pure water will weigh 1.0g and has an SG of 1.0. 1ml of Phosphoric Acid 75% weighs 1.58g so phosphoric acid at 75% is 1.58 times the weight of water and has an SG of 1.58. Therefore 1,000L will weigh 1,580kg (1000 x 1.58 = 1580). SG is usually measured at a standard temperature of 25 degrees Celsius (77F).

Sometimes you will find the SG of a concentrate is listed on the label. If not you are able to measure the SG by taking a precise liquid volume of the solution and weighing it. So, for example, if you take 500mL of a solution and weigh it and it weighs 650g you divide the volume by the weight and get an SG of 1.3. I.e. 500ml of liquid weighs 650grams. Therefore 650 ÷ 500 = 1.3 (SG)

Re ppm Meters

It is important to note that all ppm (TDS, Total Dissolved Solids) pens first measure in EC (electric conductivity) and then run a conversion program to display the reading in ppm. It is important to note that there are three different conversion factors (standards) that various manufacturers use for converting from EC to ppm. These can be simply stated as:

USA 1 ms/cm (EC 1.0 or CF 10) = 500 ppm
European 1 ms/cm (EC 1.0 or CF 10) = 640 ppm
Australian 1 ms/cm (EC 1.0 or CF 10) = 700 ppm

For example,

Hanna, Milwaukee 1 ms/cm (EC 1.0 or CF 10) = 500 ppm
Eutech 1 ms/cm (EC 1.0 or CF 10) = 640 ppm
Truncheon 1 ms/cm (EC 1.0 or CF 10) = 700 ppm

Be sure to read the manufacturers specs sheet re the conversion methods they use in converting EC to ppm.

Reduce Concentration of Formula using HydroWare

Reduce by %                  

  To establish new targets for reformulation enter the % you wish to dilute the concentrate by. New targets will appear in red in the 'Guaranteed Analysis' fields. New dilution rates will also appear in the 'Dilution rate at mL/L' and 'mL per US Gallon' fields. I.e. if you were to formulate a 50% less concentrated solution you would need to double the dilution rate of the new (half strength) formula to achieve optimum ppm in feed solution. Read more...