EC to PPM Converter
Input EC Reading
Select Conversion Scale
Selected Scale TDS PPM
All Scales Comparison
| Scale | Factor | TDS ppm |
|---|---|---|
| 0.5 (NaCl, Hanna) | 0.5 | --- |
| 0.64 (Eutech) | 0.64 | --- |
| 0.7 (442, Truncheon) | 0.7 | --- |
Formula: ppm = EC in µS/cm × factor
*EC assumed temperature-compensated to 25 °C.
Understanding EC to PPM Conversions
For hydroponic growers, aquarists and water-treatment techs whose Hanna, Eutech and Bluelab-style meters disagree — they see numbers like "1.4 EC" and "980 ppm" for the same tank and need to convert between them without guessing the meter's factor. This converter helps clarify the relationship between electrical conductivity (EC) and Total Dissolved Solids (TDS) in parts per million (ppm) for the three most common meter scales: 0.5 (NaCl, Hanna), 0.64 (Eutech), and 0.7 (442, Truncheon). Understanding these differences is crucial for accurate nutrient management and water quality monitoring.
This tool converts electrical conductivity to TDS ppm on the three meter scales: 0.5 (NaCl, Hanna), 0.64 (Eutech), 0.7 (442, Truncheon). It empowers you to cross-reference readings from different meters or to convert a given EC value to its equivalent ppm across the various industry standards.
How to Use This Converter
- Type your EC reading: Enter your electrical conductivity value into the number field.
- Choose the unit: Select the unit your meter displays — either µS/cm or mS/cm (note that 1 mS/cm = 1000 µS/cm).
- Select the conversion scale: Pick the factor your meter uses: 0.5, 0.64 or 0.7.
- Read the ppm figures: The large display shows the ppm for your chosen scale, and the table provides a comparison across all three.
- Check the formula: Review the underlying formula and record the ppm value for your records.
FAQ
Q: How do I convert EC to ppm?
A: Multiply EC in µS/cm by your meter's factor — 0.5 (NaCl/Hanna), 0.64 (Eutech) or 0.7 (442/Truncheon). So 1.4 mS/cm = 1400 µS/cm, which is 700 ppm on 0.5, 896 ppm on 0.64 and 980 ppm on 0.7.
Q: Which EC to ppm conversion factor should I use?
A: Use whichever factor your own meter uses, otherwise your numbers won't match your equipment: Hanna-style NaCl meters use 0.5, Eutech/Thermo meters use 0.64, and 442-standard meters such as the Bluelab Truncheon use 0.7.
Q: Is EC the same as TDS in ppm?
A: No — EC is a physical measurement in µS/cm or mS/cm, while ppm is a derived estimate that assumes an ion mix. The 442 scale reflects a standard of 40% sodium bicarbonate, 40% sodium sulfate and 20% sodium chloride; the 0.5 scale assumes essentially pure NaCl.
Q: Why does my ppm reading disagree with my EC reading on the same solution?
A: Because the meter stores EC internally and applies its own factor — a 1.0 mS/cm solution reads 500 ppm on 0.5, 640 ppm on 0.64 and 700 ppm on 0.7. Temperature also shifts EC by roughly 2% per °C away from 25 °C, which is why EC is normally quoted temperature-compensated to 25 °C.