EC & PPM Calculator for Cannabis
Use this EC and ppm calculator to dilute or strengthen your nutrient solution to match your plant’s growth stage — a starting point you fine-tune from there.
Calculated with PlantClue
Why EC shows how “strong” your nutrients are
Why?
EC (electrical conductivity) measures the total amount of nutrients dissolved in your water — more precisely, how many charged minerals the solution contains. Every growth stage needs a different concentration — too little slows development, too much burns the roots and blocks nutrient uptake.
Why does it matter?
An EC that’s too high is one of the most common causes of nutrient burn and brown leaf edges. An EC that’s too low often looks like a nutrient deficiency even though you fed enough — because the concentration is too weak for the current stage.
Important note
This calculation is a starting point, not exact chemistry. Always measure EC again after diluting or strengthening. This calculator works in ppm on the 500 scale (ppm = EC in mS/cm × 500); meters on the 700 scale use EC × 700.
EC Chart: Target Values & ppm Conversion
Target ranges by growth stage and the conversion between EC (mS/cm) and ppm — different meters use different scales.
| Growth stage | Target EC range |
|---|---|
| Seedling / clone | 200–400 ppm (0.4–0.8 mS/cm) |
| Vegetative stage | 500–800 ppm (1.0–1.6 mS/cm) |
| Early flower | 800–1,100 ppm (1.6–2.2 mS/cm) |
| Late flower / flush | 0–200 ppm (0.0–0.4 mS/cm) |
| EC (mS/cm) | ppm (500 scale, US) | ppm (700 scale, EU) |
|---|---|---|
| 0.4 | 200 | 280 |
| 0.8 | 400 | 560 |
| 1.0 | 500 | 700 |
| 1.2 | 600 | 840 |
| 1.6 | 800 | 1,120 |
| 2.0 | 1,000 | 1,400 |
| 2.2 | 1,100 | 1,540 |
Always check which scale your own meter uses before you copy target values from the internet — both scales are in common use.
Download the EC chart as a PDFWhat can go wrong when you dial in EC
- Ignoring your tap water EC: water that already reads 200 ppm (0.4 mS/cm) plus a standard nutrient dose can jump straight to 900 ppm (1.8 mS/cm) — if you don’t account for that baseline, you’ll overfeed every time
- Confusing runoff EC with nutrient solution EC: the runoff reading after watering is higher than your input EC (salt buildup in the growing medium) and can’t be compared directly with your nutrient solution
- Mixing ppm and EC values: 1.5 mS/cm ≠ 1.5 ppm — stick to one unit and know your meter’s scale (500 vs. 700 factor)
- Feeding during the flush: flushing is meant to clear built-up salts from the growing medium — keep EC as low as possible (0–200 ppm, 0.0–0.4 mS/cm) and don’t strengthen the solution any further
Cannabis EC — FAQ
What does EC mean for cannabis?
EC (electrical conductivity) measures how well water conducts electricity — the more nutrient salts are dissolved, the more conductive the solution. That makes EC a direct measure of how strong your nutrient solution is. Unit: mS/cm (millisiemens per centimeter); US meters usually also show it as ppm on the 500 scale.
What is the right EC for cannabis?
It depends on the growth stage: seedling/clone 200–400 ppm (0.4–0.8 mS/cm), vegetative 500–800 ppm (1.0–1.6 mS/cm), early flower 800–1,100 ppm (1.6–2.2 mS/cm), late flower/flush 0–200 ppm (0.0–0.4 mS/cm). The calculator shows whether your target EC is in the safe range for the stage you choose.
EC or ppm — what’s the difference?
ppm (parts per million) is a different unit for the same measurement. Depending on the meter, a different conversion factor is used: 500 scale (USA) = EC × 500, 700 scale (Europe) = EC × 700. Example: EC 1.5 mS/cm = 750 ppm (500 scale) or 1,050 ppm (700 scale). Always check your own meter’s scale before you copy values from the internet.
Why do I need to enter my tap water EC?
Depending on where you live, tap water has an EC of about 50–300 ppm (0.1–0.6 mS/cm) from natural minerals. That baseline counts toward your feeding target — if your water already reads 200 ppm (0.4 mS/cm) and you want 800 ppm (1.6 mS/cm), your nutrients only need to add 600 ppm (1.2 mS/cm). Leave this out and you’ll overfeed every time.
What should I do if my EC is too high?
Dilute with EC-free water (reverse osmosis water or rainwater). The calculator above shows you how much extra water to add to your nutrient solution. Always measure again after diluting — the formula is a starting point, not an exact result.
