How this calculator works
Label percentages are mass fractions. Conventional fertilizer P and K figures refer to P2O5 and K2O equivalents; this tool uses factors 0.4364 and 0.8301 to estimate elemental P and K. Custom elemental labels skip that conversion. A target for one element sets the product dose and therefore the concentrations of all other elements. Use the actual guaranteed analysis: nominal product presets do not represent every commercial formulation. Mass per volume is calculated for the final diluted volume, with no injector ratio.
Formula
Element mass = fertilizer mass × elemental fraction. Fertilizer mass (kg) = target (mg/L) × final volume (m3)/(1000 × fraction). Product rate (g/L) = kg fertilizer/m3 solution. Molarity (mol/L) = mg/L divided by (1000 × atomic mass).
Worked example
To make 10 L at 100 mg/L nitrogen using a 20% N product, supply 1 g N and dissolve 5 g fertilizer. The product rate is 0.5 g/L. A 10% N product needs 10 g for the same solution.
Advertisement
Frequently asked questions
Does ppm always equal mg/L?
They are numerically close only for dilute aqueous solutions with density near 1 kg/L. This tool calculates mg/L; concentrated stock solutions can differ.
Will the other nutrients match their targets?
Usually not exactly. Setting one element fixes the whole product dose. Review the nutrient table before using a formulation.
Does fertilizer dissolve completely?
The calculation assumes full dissolution and availability. Solubility, precipitation, source-water minerals and compatibility need separate checks.