Calculators for Monitoring and Adjusting Water Soluble Fertilizer


Sometimes calculating injector ratios, electrical conductivity (EC), and ppm N for fertilizer can be tricky.  The fertilizer label only gives measurements for a few concentrations and finding the ones in the middle needs some math.   Use these calculators for the following situations.


To get all of these calculators in a mobile format, click here.

Video Tutorial

How to use Greenhouse Fertilizer Calculators


Remember, clear water has an EC, but this EC doesn’t contribute to fertility, so it needs to be considered in these calculations.

Different fertilizers have different EC levels for the same nitrogen concentration, so you need to know from the label at least one EC for a given concentration.  Calculators 1 & 3 won’t help if you don’t have a label!

For calculators to help with mixing fertilizer, see this resource.

 Calculator 1:  What should the EC be for a certain fertilizer concentration?

Note: The final EC will be the EC of the fertilizer plus the EC of the clear water.

 Calculator 2:  How should I adjust my injector to get the EC I want? 

Note: “Target EC” might come from the fertilizer bag, or it can be calculated using Calculator 1. In Calculator 1 just put 0 for “What is the EC of the clear water only?”.

 Calculator 3:  What is the nitrogen concentration of my fertilizer?


Landscape & Greenhouse Field Specialist
Extension Field Specialist, Landscape & Greenhouse
Office: Coop Extension, Taylor Hall, Durham, NH 03824