TDS Calculator for Total Dissolved Solids in Water

Total dissolved solids, commonly shortened to TDS, describes the combined concentration of dissolved inorganic salts and small amounts of dissolved organic material in water. Typical contributors include calcium, magnesium, sodium, potassium, bicarbonate, chloride, sulfate, nitrate, and silica. TDS is often reported in milligrams per liter or parts per million. For dilute water solutions, those two numerical units are approximately equivalent because one liter of water has a mass close to one kilogram. This calculator supports two common approaches. The conductivity method estimates TDS by multiplying electrical conductivity in microsiemens per centimeter by a conversion factor. Dissolved ions carry electrical current, so conductivity is correlated with ionic concentration. The factor is not universal: values from about 0.5 to 0.7 are frequently used, while unusual water chemistry may require a factor outside that range. A factor calibrated against gravimetric measurements from the same water source gives a more defensible estimate than a generic setting. The mass and volume method represents a gravimetric determination. A known volume of filtered sample is evaporated under a defined procedure, and the remaining dissolved residue is weighed. Dividing residue mass in milligrams by sample volume in liters gives milligrams per liter. Careful filtration, drying temperature, balance calibration, contamination control, and complete removal of water affect the result. Volatile dissolved substances may be lost during heating, while insufficient drying may leave water in the residue. TDS is a broad water-quality indicator rather than an identification of individual contaminants. The same TDS can arise from very different dissolved substances and therefore does not by itself establish safety, taste, salinity, hardness, or suitability for a particular organism or process. Conductivity also responds mainly to ions and may underestimate nonionic dissolved material. Regulatory limits and recommended ranges depend on jurisdiction and use, including drinking water, aquariums, hydroponics, boilers, irrigation, and industrial processes. Use measurements corrected or standardized for temperature when possible because conductivity changes with temperature. Select the method that matches the available observation, preserve the correct units, and report whether the value is measured gravimetrically or estimated from conductivity. For important decisions, compare results with an approved laboratory method and interpret them alongside pH, hardness, alkalinity, specific ions, and other relevant water-quality tests.