TDS Calculator
Estimate dissolved solids in water by applying a conductivity-to-TDS conversion factor and temperature correction.
Typical range: 0.5 - 0.7 depending on water type.
Used for automatic 2 percent per degree C correction relative to 25 C.
TDS estimate
325 mg/L
Temperature-corrected EC
500 uS/cm
How to Use This Calculator
Measure electrical conductivity
Use a conductivity meter to obtain EC in microsiemens per centimeter (uS/cm).
Select a conversion factor
Choose a factor based on water type - for example 0.55 for pure water or 0.65 for drinking water.
Enter solution temperature
Provide temperature for automatic correction to the 25 C reference.
Review TDS estimate
The calculator reports approximate total dissolved solids in mg/L and the corrected EC.
Formula
EC25 = EC_measured / [1 + 0.02 (T - 25)]
TDS (mg/L) = EC25 x factor
A 2 percent per degree C temperature coefficient is commonly used for conductivity correction. Adjust if your meter specifies a different value.
Example
An EC of 500 uS/cm at 30 C with factor 0.65 gives EC25 about 454.5 uS/cm and TDS about 295 mg/L.
Full Description
Total dissolved solids (TDS) indicate the concentration of dissolved ions in water. Conductivity measurements are often converted to TDS using empirical factors that reflect the water's ionic composition.
The calculator applies a temperature correction and a user-selected conversion factor to generate quick TDS estimates without gravimetric testing.
Frequently Asked Questions
Why do conversion factors vary?
Different ionic compositions conduct electricity differently. Choose a factor aligned with your water type or instrument calibration.
Is this a precise measurement?
No. It provides an estimate. Laboratory gravimetric methods are more accurate for regulatory reporting.
Can I change the temperature coefficient?
Yes. Adjust the formula if your conductivity meter uses a coefficient other than 2 percent per degree C.
Does this work for seawater?
Seawater requires specialized factors. This calculator suits freshwater or drinking water ranges below about 2000 mg/L.
What units are reported?
TDS is reported in mg/L (equivalent to ppm for water-like densities). Conductivity remains in uS/cm.