TDS total dissolved solids

TDS = total dissolved solids is a measure of the dissolved salt content of freshwater. This parameter is usually measured via the conductivity and is converted to the TDS unit in the instrument.

Mostly the dissolved salt content is given in ppm (part per million). This is almost equivalent to the unit mg/l. It is possible to convert the ppm (TDS) unit to µS/cm (conductivity). However, there are different conversion factors. Therefore it is more useful to indicate the electrical conductivity instead of the salinity of a theoretical salt solution.

Europe: µS/cm * 0.64 = ppm
USA (KCl scale): µS/cm * 0.55 = ppm
USA (NaCl scale): µS/cm * 0.50 = ppm
Australia: µS/cm * 0.70 = ppm