Estimate total dissolved solids from ions or conductivity
A TDS calculator provides two clearly separated ways to estimate total dissolved solids in water. In ion-sum mode, enter measured dissolved constituent concentrations and add them on a common mg/L basis. In conductivity mode, enter electrical conductivity and an empirical conversion factor to estimate TDS. The result always states which method was used because a laboratory constituent sum and an EC conversion are not interchangeable measurements.
Total dissolved solids is a broad mass-concentration concept, not the name of one chemical. It may include dissolved mineral ions, salts, metals, and some dissolved organic material, depending on the sample and analytical definition. TDS can help describe salinity, scaling potential, taste, process-water consistency, or the loading presented to treatment equipment, but one total cannot identify which substances are present or whether any particular contaminant exceeds a limit.
Add measured ion concentrations on one basis
The constituent method uses TDS = Σci, where every ci is a measured dissolved concentration in mg/L. If a report lists 30 mg/L calcium, 12 mg/L magnesium, 80 mg/L sodium, 45 mg/L chloride, and 120 mg/L bicarbonate, the entered sum is 287 mg/L. The calculator keeps the individual rows visible so a copied total can be traced back to the measurements included.
Convert all entries to mg/L before adding them. A value in µg/L must be divided by 1,000, while g/L must be multiplied by 1,000. Do not add alkalinity reported “as CaCO3” to separately listed bicarbonate without converting and checking for duplication. Likewise, a charge-balance result, hardness value, or conductivity reading is not another constituent concentration to add to the same ion list.
Convert electrical conductivity to an approximate TDS
Conductivity mode uses TDS ≈ k × EC under the common convention of EC in µS/cm and TDS in mg/L. The factor k is visible and adjustable because it depends on the dissolved-ion mixture, temperature treatment, and instrument convention. A range around 0.5 to 0.8 is often used for rough estimates, while the default 0.67 is only a starting assumption rather than a universal water constant.
For example, an EC of 600 µS/cm with k = 0.67 gives an estimated TDS of 402 mg/L. Using k = 0.50 on the same reading gives 300 mg/L, which shows how strongly the assumption affects the result. Confirm whether the conductivity is temperature-compensated and whether a meter reports a manufacturer-specific TDS factor before comparing its display with this calculation.
Interpret and check a TDS result responsibly
For an ion sum, inspect whether the major expected cations and anions were included, whether units match, and whether any species were counted twice under different reporting bases. For an EC estimate, divide the displayed TDS by EC to recover k. A zero-conductivity reading should not be treated as proof that a real sample contains absolutely no dissolved material, and a high total does not reveal which constituent caused it.
The United States EPA lists 500 mg/L TDS as a non-enforceable secondary drinking-water guideline associated mainly with aesthetic and technical effects such as taste, deposits, staining, or scaling. It is not a health-based pass/fail boundary and does not establish that water below it is safe. Drinking-water safety requires contaminant-specific analysis, applicable local standards, representative sampling, and qualified interpretation.
Measurement limits, water decisions, and privacy
A complete gravimetric TDS method, a laboratory ion balance, and a conductivity conversion can produce different values because they observe different aspects of the sample. This calculator does not correct for filtration, volatile residues, incomplete ion coverage, temperature, electrode calibration, dissolved gases, or matrix effects. Do not use it alone to approve drinking water, diagnose treatment performance, size equipment, or make medical, environmental, agricultural, or regulatory decisions.
The values are calculated in the current browser tab. NexaCurrent does not upload the quantities, formulas, chemical names, element choices, or other information entered here, and no account is needed. Copying is a deliberate action after the answer and working are visible. Refreshing or leaving the page clears the current calculation, so keep a copied result if it is needed for later study.