Hydroponics Nutrient Solution Calculator
Calculate how much nutrient concentrate to add to reach your target EC.
Includes ppm conversion and EC guidance for different plant stages.
In hydroponics, plants receive all their nutrients dissolved in water. The electrical conductivity (EC) of the nutrient solution tells you how concentrated the nutrients are. Too little and plants starve; too much and they suffer from nutrient burn.
Formula:
Concentrate volume (mL) = (Target EC − Water EC) / Concentrate EC per mL/L × Reservoir volume (L)
EC (Electrical Conductivity): EC is measured in mS/cm (millisiemens per centimeter) or µS/cm. 1 mS/cm = 1000 µS/cm. Pure water has an EC near 0. Tap water typically reads 0.1–0.5 mS/cm. A strong nutrient solution reads 2.0–3.5 mS/cm.
PPM conversion: EC can also be expressed as ppm (parts per million) of dissolved solids. Two conversion standards exist:
- 500 scale (US): ppm = EC (mS/cm) × 500
- 700 scale (European/Hanna): ppm = EC (mS/cm) × 700
This calculator uses the 500 scale (most common in the US).
Typical EC targets by growth stage:
| Stage | EC (mS/cm) | ppm (500 scale) |
|---|---|---|
| Seedlings / clones | 0.8 – 1.2 | 400 – 600 |
| Vegetative growth | 1.2 – 2.0 | 600 – 1,000 |
| Early flowering | 1.8 – 2.5 | 900 – 1,250 |
| Peak flowering / fruiting | 2.0 – 3.5 | 1,000 – 1,750 |
| Late fruiting / flush | 0.5 – 1.0 | 250 – 500 |
Common concentrate EC values: Most commercial 2-part or 3-part nutrient concentrates add approximately 2.0–2.5 mS/cm per mL/L when diluted. Always check your specific product’s label for the correct concentration factor. General Hydroponics Flora Series: ~2.5 mS/cm per mL/L. Canna Nutrients: ~2.0 mS/cm per mL/L.
pH reminder: EC tells you nutrient concentration — but pH controls nutrient availability. Always adjust EC first, then check and adjust pH.
- Soil / coco: pH 6.0 – 6.5
- Deep Water Culture / NFT / Aeroponic: pH 5.5 – 6.0
Important: Always mix nutrients into water — not water into nutrients. Start with a clean reservoir, add your base water, then add nutrients while stirring.