TDS Converter & Water Quality Calculator
Convert between TDS, electrical conductivity, and resistivity. Identify your water quality classification and recommended treatment.
Default 0.64 works for most natural water. Adjust for specific mineral compositions.
Conversion Results
Water Quality Scale (TDS ppm)
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How do you convert TDS to electrical conductivity?
TDS (ppm) is approximately equal to Electrical Conductivity (µS/cm) multiplied by a conversion factor, typically 0.64 for most natural water sources. The exact ratio varies from 0.55 to 0.80 depending on the dissolved mineral composition. Use the slider above to adjust the factor for your specific water type.
What TDS level is safe for drinking water?
The EPA secondary standard for drinking water is 500 ppm TDS. Water below 300 ppm is considered excellent, 300–500 ppm is good, and above 500 ppm may have taste or odor issues. The WHO guideline is also 500 ppm for palatability. Industrial and process water applications often require much lower TDS levels.
What is the relationship between TDS and resistivity?
TDS and resistivity have an inverse relationship. High-purity water with very low TDS has high resistivity (up to 18.2 MΩ·cm for ultrapure water). Resistivity in MΩ·cm equals 1 divided by conductivity in µS/cm (multiplied by 10&sup6;). As TDS increases, resistivity decreases.