Simple NPK Nutrient Calculator
Pick a crop and growth stage to see its target nitrogen, phosphorus, and potassium concentrations — then scale them to your reservoir size and feed strength.
| Nutrient | Target | Elemental mass |
|---|---|---|
| NNitrogen | 75 ppm | 1.5 g |
| PPhosphorus | 22 ppm | 0.44 g |
| KPotassium | 100 ppm | 2.0 g |
| Total N-P-K | 197 ppm |
This is what your EC/TDS meter should read in the finished solution. It is not the sum of the per-element ppm (mg/L) in the table above.
Targets from: Truleaf plant database.
Elemental mass is the target amount of each element in solution — not a dose of any specific fertilizer product. Convert to product weights using your fertilizer's guaranteed analysis, and always confirm with an EC meter.
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Truleaf Simple NPK Nutrient Calculator — free at truleaf.org
How it works
The calculator reads Truleaf's per-stage nutrient targets and scales them to your setup.
- 1Choose your crop and its current growth stage. Each stage has its own nitrogen, phosphorus, and potassium targets in ppm (mg/L).
- 2Enter your reservoir volume in liters or US gallons.
- 3Set feed strength — 100% for full strength, or lower (e.g. 50%) for seedlings and sensitive stages.
- 4The tool shows target concentrations, the elemental mass of N, P, and K to reach them, and the reference EC and pH ranges for that stage.