Hydroponics Nutrient Calculator
Calculate the correct nutrient solution concentration (EC and PPM) for hydroponic plants by growth stage.
Hydroponic nutrients must be precisely measured since plants have no soil buffer to compensate for errors. The two key measurements are EC (Electrical Conductivity) and PPM (Parts Per Million), which indicate the total dissolved nutrient concentration in the water.
EC and PPM Relationship:
PPM (500 scale) = EC × 500
PPM (700 scale) = EC × 700
Note: There are two PPM scales in use. The 500 scale (TDS) is used in the United States. The 700 scale (CF) is used in Europe and Australia. Always check which scale your meter uses.
Optimal EC Ranges by Plant Type and Growth Stage:
| Plant Type | Seedling | Vegetative | Flowering/Fruiting |
|---|---|---|---|
| Lettuce / Leafy greens | 0.8–1.0 | 1.2–1.6 | 1.2–1.6 |
| Herbs (basil, cilantro) | 0.8–1.0 | 1.0–1.4 | 1.0–1.6 |
| Tomatoes | 0.8–1.0 | 1.5–2.5 | 2.5–3.5 |
| Peppers | 0.8–1.0 | 1.5–2.0 | 2.0–3.0 |
| Cucumbers | 0.8–1.0 | 1.5–2.0 | 1.7–2.5 |
| Strawberries | 0.8–1.0 | 1.0–1.5 | 1.2–1.8 |
Essential Nutrients (N-P-K and micronutrients):
| Nutrient | Role | Deficiency Symptom |
|---|---|---|
| Nitrogen (N) | Leaf growth, green color | Yellow lower leaves |
| Phosphorus (P) | Root development, flowering | Purple/dark leaves |
| Potassium (K) | Overall health, disease resistance | Brown leaf edges |
| Calcium (Ca) | Cell wall structure | Blossom end rot, tip burn |
| Magnesium (Mg) | Chlorophyll production | Yellowing between leaf veins |
| Iron (Fe) | Chlorophyll synthesis | Yellow new growth |
| Sulfur (S) | Protein formation | Pale green leaves |
Mixing Nutrient Solutions: Most commercial hydroponic nutrients come as 2-part or 3-part liquid concentrates. The standard mixing process:
- Fill reservoir with water and check base water EC (tap water typically 0.2–0.5 EC)
- Add Part A, mix thoroughly
- Add Part B, mix thoroughly (never mix concentrates together undiluted)
- Check EC and adjust — add more nutrient to raise EC, add water to lower EC
- Check pH and adjust to 5.5–6.5 range
Dosage Formula:
Amount of nutrient (mL) = Target EC increase × Reservoir volume (L) / Nutrient concentration factor
Most commercial nutrients provide a concentration factor on the label (e.g., “5 mL per liter for EC 1.0”). Use this as your baseline and adjust.
pH Management:
Optimal pH: 5.5–6.5 for most hydroponic crops
| pH Range | Nutrient Availability |
|---|---|
| Below 5.0 | Toxic levels of some minerals, lockout of calcium |
| 5.5–6.5 | All nutrients available, optimal range |
| Above 7.0 | Iron, manganese, zinc become unavailable |
Water Temperature: Nutrient solution should be maintained at 65–72°F (18–22°C). Cold water reduces nutrient uptake. Warm water above 75°F (24°C) reduces dissolved oxygen and encourages root disease (especially Pythium). Use a water chiller in warm climates.
Reservoir Management:
- Change nutrient solution completely every 7–14 days
- Top off with plain water between changes (evaporation concentrates nutrients)
- Monitor EC daily — if EC rises, plants are drinking more water than nutrients (add water); if EC drops, plants are feeding heavily (add nutrients)
- Keep the reservoir covered to block light and prevent algae growth
Starting Tip: When in doubt, start with lower nutrient concentration and increase gradually. It is much easier to correct a nutrient deficiency than nutrient burn (toxicity). Young plants and seedlings are especially sensitive to high EC.