ppm tutorial

Copied from Grubbycup's website:

How to calculate PPM:

PPM is an abbreviation for "Parts per Million", a often misunderstood and misused term of some ill repute. To clarify, I mean one part of a substance to a million parts of solution, a 1 to 1,000,000 ratio.

Nutrient solutions are mostly water, with a little bit of fertilizer added.

Water is considered to be the solvent since it is what the nutrient solutes are dissolved into to form the nutrient solution. The nutrient solution is considered to be aqueous because the primary component is water. How much is added determines the concentration.

PPM is a measure of concentration, and is used to determine how much of a nutrient should be added to reach a given nutrient level.

To keep things simple, I'll walk you through the calculations using a liter of water for the solvent. The end result can be multiplied by 3.78541 to calculate for a gallon. Each 5 ml increment is marked for the nutrient solutes, which is an even swap for a teaspoon (3 teaspoons to the tablespoon). Note it will allow for non water soluble nutrient mixtures.

So let's get started:

Gentle Reader, there is a theoretical liter of crystal clear water in cyberspace awaiting you. What would you like to add?

*** I selected 1mg of flora grow from the options

With a labeled NPK value of 2.0-1.0-6.0:

FloraGrow - General Hydroponics is made of 2.0 percent Nitrogen(N), so 1 mg (ml) contains 0.02 mg elemental N.
(Listed N value divided by one hundred to convert to decimal times the amount : 2.0/100*1 mg (ml))

It also has the equivalent to 1.0 percent Phosphorus Oxide (P2O5). Substituting the P values for the N values and using the same formula as above (1.0 / 100 * 1) we find that 1 mg (ml) contains 0.01 mg of Phosphorus Oxide, 0.00436 mg (43.6%) of which is elemental P.

The listed K value is the equivalent value to 6.0 percent Potassium Oxide (K2O). Substituting again for the K values (6.0 / 100 * 1) we find that 1 mg (ml) contains 0.06 mg of Potassium Oxide, 0.0498 mg (83%) of which is elemental K.

Gentle Reader, in a nutshell 1 ml/mg of FloraGrow - General Hydroponics contains:

0.02 mg elemental N
0.00436 mg elemental P
0.0498 mg elemental K

Now to compute the concentration:

To figure the total mass, add weight of the liter of water (1,000 mg) and the weight of what was added to it (1 mg) for a total of 1,001 mg (slight density estimation here).

Dividing the amount of solute in the solution by the total weight, and multiplying the result by one million will give the parts per million (PPM).

In this example:

Adding 1 mg (ml) of FloraGrow - General Hydroponics to 1 liter of water will result in:

0.02 mg / 1,001 mg * 1,000,000 = 20 PPM of elemental N.
0.00436 mg / 1,001 mg * 1,000,000 = 4 PPM of elemental P.
0.0498 mg / 1,001 mg * 1,000,000 = 50 PPM of elemental K.

To prepare one gallon at this strength use 4 ml/mg of FloraGrow - General Hydroponics.