Hydroponic Nutrient Calculator
Build balanced hydroponic nutrient solutions for 10 indoor farming crops. Select your crop, growth stage, and water source to get target EC, pH, and macro/micronutrient concentrations with A/B tank formulations.
How Hydroponic Nutrient Solutions Work
Hydroponic nutrient solutions deliver all essential mineral elements directly to plant roots in water. Unlike soil, where nutrients are buffered by organic matter and microbial activity, hydroponic systems require precise control of nutrient concentration (EC), acidity (pH), and individual element ratios. Plants need six macronutrients (N, P, K, Ca, Mg, S) and six micronutrients (Fe, Mn, Zn, B, Cu, Mo) in specific proportions that change by crop species and growth stage. Solutions are typically mixed in two concentrated stock tanks (A and B) to prevent calcium from precipitating with sulfates and phosphates.
How to Use This Calculator
- 1 Select your crop and growth stage. Each combination has different EC, pH, and nutrient ratio targets.
- 2 Choose your water source. RO water starts from zero; municipal and well water contribute baseline calcium, magnesium, and sulfur that offset fertilizer needs.
- 3 Review the target nutrient concentrations (ppm) for all 12 mineral elements.
- 4 Use the A/B tank formulation to build your concentrated stock solutions with the recommended fertilizer salts.
Target EC & pH by Crop & Growth Stage
| Crop | Stage | EC (mS/cm) | pH Range |
|---|---|---|---|
| Butterhead | Propagation | 0.5 | 5.5–5.8 |
| Butterhead | Grow-out | 1.2 | 5.5–6.0 |
| Butterhead | Harvest | 1.3 | 5.8–6.0 |
| Romaine | Propagation | 0.5 | 5.5–5.8 |
| Romaine | Grow-out | 1.4 | 5.5–6.0 |
| Romaine | Harvest | 1.5 | 5.8–6.0 |
| Basil | Propagation | 0.5 | 5.5–6.0 |
| Basil | Vegetative | 1.4 | 5.5–6.5 |
| Basil | Harvest | 1.6 | 5.5–6.5 |
| Strawberry | Establish | 1.0 | 5.5–6.0 |
| Strawberry | Flower | 1.5 | 5.5–6.0 |
| Strawberry | Fruit | 1.8 | 5.5–6.0 |
| Tomato | Transplant | 1.5 | 5.5–6.0 |
| Tomato | Vegetative | 2.2 | 5.5–6.5 |
| Tomato | Fruiting | 2.8 | 5.8–6.3 |
| Microgreens | Blackout | 0.0 | 5.5–6.0 |
| Microgreens | Light | 0.6 | 5.5–6.0 |
| Microgreens | Harvest | 0.8 | 5.5–6.0 |
Frequently Asked Questions
Why do hydroponic nutrients need A and B tanks?
Calcium nitrate (the primary calcium source) reacts with sulfates and phosphates in concentrated form, creating insoluble precipitates that clog lines and remove nutrients from solution. Separating calcium into Tank A and sulfates/phosphates into Tank B prevents this. The two concentrates mix safely only when diluted in the working reservoir.
What EC should I target for lettuce?
Lettuce propagation uses 0.5 mS/cm. Grow-out ranges from 1.0–1.5 mS/cm depending on variety. Butterhead tolerates the lower end (1.2), while romaine benefits from higher EC (1.4–1.5) for dense heart formation. Drop EC before harvest to reduce bitterness and improve shelf life.
How does water source affect nutrient mixing?
Municipal and well water contain baseline minerals — primarily calcium, magnesium, and sulfur. These must be subtracted from your target recipe to avoid over-supplying. RO or distilled water starts at zero, giving you full control. Hard well water (120+ ppm Ca) may require reducing or eliminating calcium nitrate from Tank A.
How often should I test my nutrient solution?
EC and pH should be checked daily in recirculating systems. Full water analysis (individual element concentrations) should be done weekly or bi-weekly. As plants absorb nutrients at different rates, ratios drift over time even if EC stays stable. Periodic dump-and-refill (every 7–14 days) resets the solution to target ratios.
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