Nutrient Calculator.
Nutrient Calculator
Build a fertilizer recipe from raw compounds. See elemental ppm delivery with compatibility flagging.
How to read this
The calculator works at the compound level, not the product level. A commercial fertilizer like "Brand X Bloom A" is a recipe of compounds at known concentrations; if you know what compounds are in it (label or SDS), you can replicate it from raw chemistry.
For each compound at a given concentration (mg/L), the calculator computes how many ppm of each element that compound contributes. Sum across all compounds in your recipe = elemental delivery in your final solution.
Concentration units
The calculator uses mg/L (also called ppm of the compound itself) as the input unit. To convert from typical recipe formats:
| From | Conversion |
|---|---|
| g/L (grams per liter) | × 1000 → mg/L |
| g/gal (grams per gallon) | × 264.17 → mg/L (US gallon) |
| tsp/gal | compound-density-dependent; consult label |
| oz/gal | × 7489.15 → mg/L (US fluid ounce → mg/L) |
For dry compounds, the conversion is straightforward: 1 gram dissolved in 1 liter = 1000 mg/L. For pre-formulated liquid products, consult the label.
Common tank-mix incompatibilities
- Calcium + phosphate in concentrated stock: forms calcium phosphate precipitate. Always separate Ca from PO₄ in concentrate tanks.
- Calcium + sulfate at high concentration: forms calcium sulfate (gypsum) precipitate. Acceptable in dilute final solution but not concentrated stock.
- Iron chelates + phosphate at high concentration: chelate breakdown reduces Fe availability.
- Magnesium + phosphate at high concentration: similar to Ca + PO₄ but milder.
- Nitric acid + chlorides: produces nitrosyl chloride; avoid mixing.
The standard split for hydroponic recipes is two tanks: A (Ca, micronutrients with chelators) and B (PO₄, SO₄, K). They mix safely in dilute final solution.
Composition reference
| Compound | Formula | N | P | K | Ca | Mg | S |
|---|---|---|---|---|---|---|---|
| Potassium nitrate | KNO₃ | 13.8 | — | 38.7 | — | — | — |
| Calcium nitrate | Ca(NO₃)₂·4H₂O | 11.9 | — | — | 17.0 | — | — |
| Magnesium sulfate | MgSO₄·7H₂O | — | — | — | — | 9.9 | 13.0 |
| Monopotassium phosphate | KH₂PO₄ | — | 22.8 | 28.7 | — | — | — |
| Potassium sulfate | K₂SO₄ | — | — | 44.9 | — | — | 18.4 |
| Calcium sulfate | CaSO₄·2H₂O | — | — | — | 23.3 | — | 18.6 |
| Urea | (NH₂)₂CO | 46.7 | — | — | — | — | — |
| Ammonium sulfate | (NH₄)₂SO₄ | 21.2 | — | — | — | — | 24.3 |
| Monoammonium phosphate | NH₄H₂PO₄ | 12.2 | 26.9 | — | — | — | — |
Values are percent by weight of element in compound. P shown as elemental P (multiply by 2.29 for P₂O₅ form). K shown as elemental K (multiply by 1.20 for K₂O form).
Free under CC BY 4.0. Cite as "OAT Nutrient Calculator (openagriculturetechnology.com)". Compound composition data from authoritative chemistry references.