Conductivity converter

This converter changes conductivity units (including S/cm, mS/cm, µS/cm and legacy mho units) and provides an indicative TDS estimate in ppm.

Input:
S/cm
mS/cm
microS/cm
EC	mS/cm ¹⁾
CF
mho/cm
mho/m
ppm TDS

The siemens (S) is the unit of electrical conductance; conductivity is expressed per unit length, such as S/m or S/cm. A conductivity probe’s cell constant accounts for its electrode geometry. Mho is an older name for siemens, so mho/cm equals S/cm and mho/m equals S/m. In this converter, EC is shown numerically as mS/cm. CF is a meter scale rather than an SI unit; check your instrument manual for its definition. This unit conversion does not correct conductivity for temperature. 1) EC means electrical conductivity. In this converter, the EC reading is displayed in mS/cm (1 EC = 1 mS/cm). Other instruments may label or scale EC differently; check the stated units. Click here for a definition of water conductivity.

Understanding conductivity, specific conductance and TDS

Electrical conductivity describes how readily a solution conducts an electric current; dissolved ions contribute to that conduction. Specific conductance is conductivity reported at a reference temperature, commonly 25 °C. Conductivity changes with temperature, so compare readings at the same reference temperature. This converter changes units only; it does not temperature-correct a reading.

Total dissolved solids (TDS) is a mass concentration of dissolved material. Conductivity can be used to estimate TDS because dissolved ions carry current, but the relationship depends on the water’s ionic composition and concentration. A single conversion factor is not universal. For a reliable site-specific estimate, determine a factor from paired conductivity and TDS measurements across the expected water range. Where accuracy matters, measure TDS directly or determine it from an appropriate laboratory method.

The calculator’s “ppm TDS” result is therefore indicative. For dilute water, ppm is approximately equivalent to mg/L; for concentrated brines, report the concentration basis and use suitable units such as mg/L or g/L. The EC and CF labels are meter scales, not universal SI units: confirm the scale used by your instrument before comparing readings.