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The Most Comprehensive & Professional TDS Knowledge

What Is TDS?

Total Dissolved Solids (TDS) refers to the total amount of all dissolved solids in water, including minerals, salts, metal ions, etc. It is usually expressed in mg/L or ppm. There are two ways to get TDS. One is by testing the water sample in the laboratory, which can obtain the concentration of all ions in the water. This method is suitable for industrial or water treatment fields and other scenarios that require accurate ion concentration, to determine in advance which ion content in the water exceeds the standard to make the corresponding treatment in time to avoid erosion damage to equipment and instruments; the second is roughly measured by TDS measuring instrument, which works by collecting the electrical conductivity (EC) signal and then according to different ambient temperatures, converted into TDS value. It can not accurately provide the content of various types of substances contained in the water. The field of life only needs to measure the approximate TDS value. If more than the standard value can be softened by adding water purifiers and other equipment, you can avoid the phenomenon of hot water kettle scales, glass products water stains, blocked water pipes.

Water quality is being measured in the laboratory.

Water quality measurement in laboratory

TDS meter measures TDS value in a glass of water.

TDS meter for water quality measurement

The TDS value measured by the laboratory not only tells the concentration of various types of ions, but also provides some basic information about the water quality, such as the alkalinity, hardness and salinity level of the water.

It is worth noting that the TDS value can be used as an indicator of water quality, but not as an indicator of the degree of contamination. It gives you an idea of total dissolved solids, not dissolved substances.

TDS in Life

The TDS value in drinking water is mainly based on natural resources, followed by human-induced sewage, industrial waste, chemicals used in the water treatment process, and so on. High TDS values not only cause water stains on our glasses and other containers, but also create water scale at water pipes causing clogging. If the TDS value exceeds 1000 mg/L, the drinking water will be considered unfit for human consumption, and according to a study by the World Health Organization, 0 ppm – 300 ppm is the best water quality for palatability.

Pour water into a glass on a black platform
How to calculate TDS?


As an example, when the conversion factor k takes the value of 0.64, 1 μS/cm = 0.64 ppm.

To save your valuable time, our TDS & EC converter can help you perform calculations quickly.

The purer the water, the lower the electrical conductivity, the smaller the TDS, but it should be noted that the water quality can not be completely by TDS alone, such as the concentration of harmful heavy metal ions, bacteria, organic concentration, nitrite concentration, pesticide residues, etc. These can not be reflected by the TDS value, so if you encounter any water quality problems, please contact us, we can provide you with professional solutions.

Units Conversion

In the TDS calculator, when filling in the ion concentration, you will encounter different units that indicate the concentration: mg/L, ppm, mmol/L, mEq/L, etc. Here we learn about the conversion relationship that exists between these units:

Concentration unit conversion formula

For example, a Ca2+ concentration of 15 mg/L is equivalent to 15 ppm, 15 × 2 ÷ 40.078 = 0.7485 mEq/L and 15 ÷ 40.078 = 0.3743 mmol/L.

You can also select different units directly on the calculator, reducing the hassle of converting units.

Relative Atomic Masses of Common Chemical Elements
Atomic Number Chemical Elements Relative Atomic Mass Atomic Number Chemical Elements Relative Atomic Mass
1 H 1.008 17 Cl 35.450
5 B 10.811 19 K 39.098
6 C 12.011 20 Ca 40.078
7 N 14.007 25 Mn 54.938
8 O 15.999 26 Fe 55.845
9 F 18.998 28 Ni 58.693
11 Na 22.990 29 Cu 63.546
12 Mg 24.305 30 Zn 65.380
13 Al 26.982 56 Ba 137.330
16 S 32.065