Calculator
Example data table
| Plant | Stage | Typical EC range (mS/cm) | Notes |
|---|---|---|---|
| Lettuce | Vegetative | 0.8 – 1.4 | Lower range helps reduce tip burn. |
| Herbs (basil) | Vegetative | 1.0 – 1.6 | Maintain steady EC for flavor consistency. |
| Tomato | Flower/Fruit | 2.0 – 3.5 | Increase gradually; watch leaf edge burn. |
| Pepper | Flower/Fruit | 1.8 – 3.0 | Stability matters more than chasing highs. |
| Cucumber | Vegetative | 1.6 – 2.4 | Adjust with climate; higher light tolerates more. |
Formula used
1) Dosing by product strength
ΔEC = TargetEC − BaseEC
mL per L = ΔEC ÷ Strength
Total mL = (mL per L) × Volume(L)
2) Blending from a stock solution
TargetEC = (StockEC×Vs + BaseEC×(Vt−Vs)) ÷ Vt
Solving for stock volume Vs:
Vs = (TargetEC − BaseEC) ÷ (StockEC − BaseEC) × Vt
3) Temperature correction (optional)
ECref ≈ ECmeasured ÷ (1 + k×(T − Tref))
Where k is the coefficient per °C.
How to use this calculator
- Measure your base water EC before adding nutrients.
- Pick a target EC for your plant stage and system.
- Select a method: dosing, blending, or conversion.
- Enter volume and the required method-specific details.
- Press Calculate and follow the dosing steps.
- Mix well, wait briefly, and re-check EC for accuracy.
- Download CSV or PDF to keep a mixing record.
EC as a consistent mixing standard
Electrical conductivity (EC) expresses how strongly your nutrient solution conducts electricity, which closely tracks total dissolved ions. Unlike PPM scales that vary by meter, EC in mS/cm is a stable reference for mixing and troubleshooting. For example, if your base water reads 0.30 mS/cm and your target is 1.60 mS/cm, you need a 1.30 mS/cm increase from nutrients.
Understanding target EC by crop stage
Targets change with crop type, light intensity, temperature, and growth stage. Leafy greens often perform around 0.8–1.4 mS/cm, while fruiting crops commonly run higher during flower and fruit set. A practical approach is to increase EC gradually by 0.2–0.4 mS/cm per adjustment and watch plant response for 48–72 hours. Sudden jumps can cause tip burn, edge scorch, or stalled uptake.
Dosing vs blending workflows
This calculator supports two production-friendly methods. Dosing uses your measured product strength (ΔEC per 1 mL/L) to estimate an initial dose, then you verify with a meter. Blending calculates how many liters of a higher-EC stock solution you should mix with base water to hit the target in one step. Blending is useful for consistent batches, while dosing is ideal when switching products or changing recipes frequently.
| Scenario | Base EC | Target EC | Volume | Input | Output (example) |
|---|---|---|---|---|---|
| Dose | 0.30 | 1.60 | 20 L | Strength 0.10 ΔEC per 1 mL/L | 13.0 mL/L → 260 mL total |
| Blend | 0.30 | 1.60 | 20 L | Stock EC 12.0 | ~2.2 L stock + 17.8 L water |
Temperature and measurement quality
EC varies with temperature, so consistent readings depend on compensation. If your meter auto-compensates, keep it enabled and measure after mixing thoroughly. If not, the optional correction estimates what the reading would be at a chosen reference temperature (commonly 25°C). Use a clean probe, rinse between samples, and wait for the display to stabilize before recording the value.
Recordkeeping and repeatability
Professional growing benefits from repeatable recipes. Save each batch with date, crop stage, base water EC, target EC, and final verified EC. When drift occurs, check base water changes, salt buildup, and dosing accuracy. Exporting results to CSV or PDF helps you compare runs, standardize staff procedures, and quickly reproduce successful mixes in future cycles.
FAQs
1) Why does my EC drop after mixing?
Some salts dissolve slowly, and temperature changes can shift the reading. Mix thoroughly, wait 3–5 minutes, then measure again. Also confirm your meter is clean and calibrated.
2) What PPM factor should I choose?
Use the factor that matches your meter or chart (commonly 500, 640, or 700). If unsure, rely on EC for mixing, and treat PPM as an approximate reference only.
3) My target EC is below my base EC. What now?
You cannot reach a lower target by adding nutrients. Dilute with lower-EC water (RO, rain, or blended water), or reduce salts in the source water before mixing.
4) How do I find product strength (ΔEC per 1 mL/L)?
Make a 1 L test mix with your base water, add a known dose (e.g., 1–5 mL), mix well, and measure the EC increase. Divide the EC change by the dose to estimate strength.
5) Can I exceed my stock EC using the blend method?
No. Blending only dilutes a stock solution; it cannot produce a final EC higher than the stock EC. Use dosing or a stronger stock if you need higher targets.
6) Should I adjust pH before or after hitting EC?
Usually set EC first, then adjust pH. Nutrients can shift pH, so final pH correction is more stable after EC is close to target. Re-check both values after 10 minutes.
7) How accurate is the calculator’s dose estimate?
It provides a strong starting point based on your inputs, but real mixes vary by water chemistry and product formulation. Always verify with your meter and make small corrections in steps.