TDS Calculator
Our mixtures & solutions calculator computes tdscalculator accurately. Enter measurements for results with formulas and error analysis.
Reviewed by Manoj Kumar, Mathematics Educator
Formula
TDS (mg/L) = EC (uS/cm) x conversion factor
TDS is calculated by multiplying the electrical conductivity (EC) of water by a conversion factor that depends on the ionic composition. Temperature compensation adjusts the EC reading to the standard reference temperature of 25 degrees C.
Worked Examples
Example 1: Tap Water TDS
Problem:A tap water sample has an EC of 450 uS/cm at 25 deg C. Calculate TDS using a factor of 0.65.
Solution:TDS = EC x factor\nTDS = 450 x 0.65\nTDS = 292.5 mg/L
Result:TDS = 292.5 ppm (Excellent drinking water)
Example 2: Pool Water with Temperature Correction
Problem:Pool water measures 1200 uS/cm at 32 deg C. Calculate TDS at 25 deg C reference.
Solution:EC25 = 1200 / (1 + 0.02 x (32-25))\nEC25 = 1200 / 1.14 = 1052.6 uS/cm\nTDS = 1052.6 x 0.65 = 684.2 mg/L
Result:TDS = 684.2 ppm (Fair water quality)
Frequently Asked Questions
What is TDS (Total Dissolved Solids)?
Total Dissolved Solids (TDS) measures the combined concentration of all inorganic and organic substances dissolved in water. These include minerals, salts, metals, cations, and anions. TDS is expressed in milligrams per liter (mg/L) or parts per million (ppm). Common dissolved substances include calcium, magnesium, sodium, potassium, bicarbonate, chloride, and sulfate. TDS affects water taste, hardness, and suitability for various uses including drinking, irrigation, and industrial processes.
How is TDS related to electrical conductivity?
TDS and electrical conductivity (EC) are closely related because dissolved ions conduct electricity. The relationship is TDS = EC multiplied by a conversion factor, typically between 0.5 and 0.8 depending on the ionic composition of the water. A factor of 0.65 is commonly used for general purposes. Pure water has very low conductivity, while seawater has high conductivity due to its high salt content. EC is measured in microsiemens per centimeter (uS/cm) and provides a quick indirect measurement of TDS.
What TDS level is safe for drinking water?
The EPA secondary standard for drinking water is 500 mg/L TDS, though this is not an enforceable limit. Water below 300 ppm TDS is considered excellent for drinking. Between 300 and 600 ppm is good, 600 to 900 ppm is fair, and above 1200 ppm is generally considered unacceptable. Very low TDS water (below 50 ppm) may taste flat because minerals contribute to flavor. Bottled water typically ranges from 50 to 300 ppm depending on the source and treatment method.
Why does temperature affect TDS readings?
Temperature affects EC measurements because warmer water allows ions to move more freely, increasing conductivity. The standard reference temperature is 25 degrees Celsius, and a temperature coefficient of approximately 2% per degree Celsius is used for correction. If water is measured at 30 degrees C, its EC reading will be about 10% higher than at 25 degrees C. Most modern TDS meters have automatic temperature compensation, but manual correction is needed when using basic conductivity meters.
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy