EC to PPM Calculator
EC meters measure conductivity, but growers think in PPM. The catch: there is no single conversion — meters use 0.5, 0.64, or 0.7 factors. This calculator uses the common 0.5 (500) scale; know your meter before trusting the number.
Calculator
EC to PPM Calculator
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EC meters measure conductivity, but growers think in PPM. The catch: there is no single conversion — meters use 0.5, 0.64, or 0.7 factors. This calculator uses the common 0.5 (500) scale; know your meter before trusting the number.
How to use this calculator
- Enter EC in µS/cm.
- Multiply by 0.5 (500 scale).
- Read approximate PPM.
- Confirm your meter uses the 500 scale.
The formula
PPM ≈ EC × 500 ÷ 1000 = EC × 0.5 on the 500 scale.
What the units mean
µS/cm — microsiemens per centimeter, the unit of electrical conductivity (EC) that meters actually measure before converting to a PPM estimate.
PPM (parts per million) — one part of solute per million parts of the total mixture. The workhorse unit for trace concentrations in water, air, and food.
Worked example
EC of 1,600 µS/cm → 800 PPM (500 scale).
Quick reference
| EC (µS/cm) | PPM (500 scale) |
|---|---|
| 500 | 250 |
| 1,000 | 500 |
| 1,600 | 800 |
| 2,000 | 1,000 |
500 scale. Check your meter — 640 and 700 scales differ.
Where you will actually use this
Hydroponic nutrient charts are written in PPM, but most pens read EC.
- Hydroponic nutrient mixing
- Water quality screening
- Aquarium monitoring
Mistakes that give wrong answers
- Using the wrong scale factor for your meter
- Treating EC-derived PPM as a real chemical analysis
Key takeaways
- Formula: PPM ≈ EC (µS/cm) × 0.5 (500 scale)
- Remember: 500 scale. Check your meter — 640 and 700 scales differ.
- Watch out for: Using the wrong scale factor for your meter
- Next step: run your own numbers in the calculator above, then verify with a measurement — calculated values are only as good as the inputs.
Frequently asked questions
What is the EC to PPM conversion factor?
0.5 (500 scale), 0.64, or 0.7 depending on the meter.
What EC is 1000 PPM?
2,000 µS/cm on the 500 scale.
Is EC the same as PPM?
No — EC measures conductivity; PPM here is an estimate derived from it.