Nutrients & EC
What’s the difference between EC and PPM, and which one should you use?
The answer is: Use EC.
Why
Use EC as your primary nutrient-strength measurement. EC measures electrical conductivity directly, while the PPM shown on most grow meters is calculated from EC using a conversion scale. At 1.5 EC, a 500-scale meter shows 750 PPM and a 700-scale meter shows 1,050 PPM even though the reservoir is identical. EC removes that ambiguity because 1.5 EC is always 1.5 EC. If your meter uses microsiemens, 1.5 EC is 1,500 µS/cm. EC tells you total conductivity, not whether the nutrient recipe itself is properly balanced.
What to remember
- EC is the direct conductivity measurement.
- Most grow-meter PPM values are calculated from EC.
- The 500 and 700 PPM scales can show different numbers for the same reservoir.
- 1.5 EC is always 1.5 EC, or 1,500 µS/cm.
- EC measures total conductivity, not nutrient balance.
Keep growing