TDS Calculator (Total Dissolved Solids)

Total Dissolved Solids (TDS) measures the concentration of minerals, salts, and other dissolved particles in water — a key indicator of water quality for drinking, irrigation, and aquaculture. Enter your water's Electrical Conductivity (EC) and select a Conversion Factor (K) based on your water type to get your TDS in mg/L and PPM, along with a Water Quality Classification and the applied K factor. Advanced users can enter a Custom K Value for greater precision.

dS/m

Electrical conductivity in deciSiemens per meter

Select appropriate conversion factor based on water type

Enter custom conversion factor if known

Results

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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Frequently Asked Questions

What are total dissolved solids (TDS) in water?

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.

How do I calculate TDS from conductivity?

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.

What conversion factor should I use for TDS calculation?

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.

How do I convert TDS from mg/L to ppm?

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.

What are acceptable TDS levels in drinking water?

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.

Why is TDS important for water quality assessment?

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.

What units are used for electrical conductivity in TDS calculations?

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.