Using my Nutrient Calculator with Commercial Fertilizers : Part No.1

One of the main reasons why I wanted to develop a nutrient calculator for hydroponics was to allow people to understand the amount of nutrients they are adding to their solutions and to use the calculated amounts to either use common salts to achieve the same nutrient percentages or to understand which salts are needed to adequately compliment the nutrition achieved by their hydroponic nutrients. On these posts I intend to show you how you can use my hydroponic nutrient calculator with your commercial hydroponic nutrient composition, figure out the amount of nutrients given by a certain amount of the fertilizer, adapt your fertilizer to a given formulation you want, supplement your nutrient with other salts and get a similar composition yourself with easily available salts (which are used to make your hydroponic nutrients most of the time). For this tutorial you will need my hydroponic nutrient calculator available here.
First of all, lets learn how to add a given nutrient commercial fertilizer to your list of hydroponic salts/nutrients. After you open the program go to the “Nutrient Salts Used” tab and select the “Add New Salt” button. A screen will pop up in which you can input the percentage composition values of your fertilizer. As an example, let us use the FloraBloom fertilizer from general hydroponics and add it to our fertilizer list. The fertilizer composition given on the product’s label is available here. Below you can see an image of the added percentages on my nutrient calculator, note that the K2O, P2O5 check box is used as the percentage values on the label are given as oxides for K and P. After finishing the addition the “GH – FloraBloom” item becomes available in the bottom of the page.

We are now going to calculate the ppm values for the different nutrients we would get for the recommended addition of 1 tbsp/gallon for regular growth. Since 1 tbsp is 15 mL and we assume the fertilizer density to be 1 g/mL we get an addition of about 15g per gallon of solution. We input 15 in the field next to the fertilizer name, leave the purity at 100% and go to the “Salt to Formulation” tab where we input a volume of 1 gallon. We then get the results shown below. You can see that this preparation would give us around 87 ppm of P, around 131 ppm of K, 60 ppm of Mg and 40 ppm of S. Now that you know how to get these values it becomes easy for you to know the amount of nutrients you are getting for a given amount of any commercial fertilizer simply by using the composition values available on the label.

Getting these values is only the first and easiest thing we can do with commercial fertilizers using my calculator but you will see within the next few tutorials that much more powerful things are possible. Right now you can also get the ppm values of different mixes of commercial fertilizers as well as current ppm values you are getting with any custom regime you are using. For example you could upload the whole General Hydroponics series to the calculator and see the different ratios you can achieve with different proportions of their products.

On the next tutorial we are going to use the above mentioned fertilizer as well as a predetermined formula to determine which salts are needed to compliment the above solution and obtain a well-balanced custom formulation. After that we are going to see how we can use the above obtained ppm values to makeup our own copy of this fertilizer as well as how we can improve it. I hope you are enjoying my free hydroponic calculator and that you leave any comments you may have :o)



  • jesseallencollins
    June 28, 2010 @ 4:40 am

    I have the ebb n gro system fill and drain 12 buckets, 55 gal res.. if i follow the directions on my nutes they end up way over ppm like 795 up to almost 2000 do i add nutes to the 55 gal tank or to 55 seprate 1 gal bottles than dump in res…

  • Daniel
    June 28, 2010 @ 10:37 am

    Hello Jesse,

    Thank you very much for your comment :o) I don't know exactly what you mean. You should input your reservoir volume on the volume field so – in your case – this value would be 55 gallons. You will then get the concentration values of each element you get when dissolving your nutrients in your 55 gallon reservoir. However this concentration values are NOT related to the ppm levels you read with an EC meter which are TDS and have NOTHING to do with real ppm concentration levels of nutrients. The last version also gives an EC estimate in mS/cm.

    The idea is that you will be able to see the actual concentration levels of individual nutrients and this will allow you too know if you are getting too much or too little of one or several of them. For example if you are getting a P level of 80 ppm that is too high, while if you are getting a N level of 100 its too low, etc.

    I hope this helps :o) Thank you very much for using my calculator,

    Best Regards,


  • Ruben
    January 13, 2011 @ 9:39 am

    Encontre su programa ayer y la verdad que estoy impresionado, pero me salen varios errores en este paso y no se si es por algo que estoy haciendo mal o que.

    Logro ingresar el “add new salt” pero luego me dice que los valores decimales no son correctos (los he cambiado varias veces a . y , ) me puede indicar si debo insertar un punto o una coma??

    Por otro lado, cierro el pop up, selecciono el nuevo producto y voy a la pestaña de Formulacion y no me aparece nada.

    Tengo que darle a algun boton antes??

    Gracias de antemano.

    • admin
      January 14, 2011 @ 3:11 am

      Hello Ruben

      Please post comments on this blog ONLY in English,

      Best Regards,


  • mohd
    January 10, 2012 @ 1:26 pm

    thank you so much you are the best

  • Chuck
    July 14, 2016 @ 4:01 pm

    I have a quick question. In the NPK fields you can choose to enter P and K as P205 and K2O. I have 5-12-26 from JRPeters that says:

    Available Phosphate (P2O5) …12%
    Soluble Potash (K2O)……….26%

    So is it more accurate for me to put those numbers in as P205/K20 or do they already do a conversion when listing NPK and I should just use the regular P and K fields?

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