What this calculator does
Water-soluble fertilizer dosing works out fertilizer weight needed to reach a target nutrient concentration in a given volume of water. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
The inputs explained
| Field | What to enter |
|---|---|
| Target nutrient concentration (ppm (mg/L)) | A number, measured in ppm (mg/L). Starts at 200. |
| Nutrient percentage on the label (%) | A number, measured in %. Starts at 20. |
| Water volume (L) | A number, measured in L. Starts at 100. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with target nutrient concentration
Every other input is held at the calculator’s starting values while target nutrient concentration varies. Select any row to load that scenario into the calculator.
| Target nutrient concentration (ppm (mg/L)) | Fertilizer needed | Fertilizer concentration | Water volume |
|---|---|---|---|
| 100 | 50.00 g | 500.00 mg/L (g/m³) | 100.00 L |
| 150 | 75.00 g | 750.00 mg/L (g/m³) | 100.00 L |
| 200 | 100.00 g | 1,000.00 mg/L (g/m³) | 100.00 L |
| 300 | 150.00 g | 1,500.00 mg/L (g/m³) | 100.00 L |
| 400 | 200.00 g | 2,000.00 mg/L (g/m³) | 100.00 L |
| 600 | 300.00 g | 3,000.00 mg/L (g/m³) | 100.00 L |