Enter your water's Electrical Conductivity (EC) and choose a Conversion Factor (K) — or plug in a Custom K Value — and this TDS Calculator will work out your Total Dissolved Solids in PPM, the Applied K Factor used, and a Water Quality Classification so you know exactly what's floating around in your water.
Total Dissolved Solids (TDS)
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TDS in PPM
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Water Quality Classification
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Applied K Factor
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Total dissolved solids (TDS) refers to the sum of all ionic particles smaller than 2 μm dissolved in water, including organic and inorganic substances like salts, minerals, and metals. TDS is a key indicator of water quality and purity.
TDS is calculated using the formula: TDS (mg/L) = K × EC (dS/m), where K is the conversion factor and EC is electrical conductivity. The K factor typically ranges from 640-800 depending on water type.
Use K=640 for most cases, K=735 for mixed waters, and K=800 for high conductivity water (EC > 5 dS/m). If you know the specific conversion factor for your water source, use the custom option.
TDS in mg/L is numerically equal to TDS in ppm (parts per million) for water. The conversion is 1:1, so 500 mg/L equals 500 ppm.
Excellent: <300 ppm, Good: 300-600 ppm, Fair: 600-900 ppm, Poor: 900-1200 ppm, and Unacceptable: >1200 ppm. WHO guidelines recommend TDS below 1000 ppm for drinking water.
TDS indicates the concentration of dissolved substances in water, affecting taste, odor, and safety. High TDS can indicate contamination, while very low TDS may suggest over-purification or lack of essential minerals.
Electrical conductivity is commonly measured in dS/m (deciSiemens per meter), mS/cm (milliSiemens per centimeter), or μS/cm (microSiemens per centimeter). 1 dS/m = 1 mS/cm = 1000 μS/cm.