Conductivity Calculator

Calculate electrical conductivity, resistivity, and total dissolved solids (TDS) for aqueous solutions and electrolytes.

Conductivity
Resistivity
TDS
μS/cm
mS/cm
S/m
Custom Solution Parameters
Ω·cm
Ω·m
kΩ·cm
Custom Solution Parameters
Typically 1.5-2.5% per °C for most aqueous solutions
Typically 0.5-0.8, with 0.65 as a common default
mg/L (ppm)
g/L
ppt
Custom Solution Parameters
List the main ions present in your solution
Calculating...
Conductivity Calculation Results

Understanding Electrical Conductivity

Electrical conductivity is a measure of a solution's ability to conduct an electric current. It depends on the presence of ions in the solution, their concentration, mobility, valence, and temperature.

Key Insight: Pure water has very low conductivity (0.055 μS/cm at 25°C). Conductivity increases with ion concentration, making it a useful parameter for estimating total dissolved solids (TDS) in water.

Conductivity Formulas

1

Conductivity from Resistance: Conductivity (κ) = Cell Constant (K) / Resistance (R)

κ = K / R
2

Resistivity from Conductivity: Resistivity (ρ) = 1 / Conductivity (κ)

ρ = 1 / κ
3

TDS from Conductivity: TDS = Conductivity × Conversion Factor

TDS = κ × f

Where f is typically between 0.5 and 0.8, depending on the ionic composition

4

Temperature Correction: Conductivity measurements are typically standardized to 25°C using temperature compensation factors.

Common Conductivity Ranges

Solution Type Typical Conductivity Range Description
Ultra Pure Water 0.055 μS/cm Theoretical minimum at 25°C
Distilled Water 0.5 - 5 μS/cm Very low ion content
Drinking Water 50 - 500 μS/cm Varies by source and treatment
Tap Water 100 - 1000 μS/cm Contains dissolved minerals
Brackish Water 1,000 - 10,000 μS/cm Moderate salt content
Seawater 45,000 - 55,000 μS/cm High salt concentration
Concentrated Brine 100,000+ μS/cm Very high salt content

Factors Affecting Conductivity

  • Ion Concentration: More ions = higher conductivity
  • Ion Type: Different ions have different mobilities (H⁺ and OH⁻ are highly mobile)
  • Temperature: Conductivity increases with temperature (approx. 2% per °C)
  • Ion Valence: Multivalent ions contribute more to conductivity
  • Solution Viscosity: Higher viscosity reduces ion mobility
  • Ion Pairing: Formation of ion pairs reduces effective ion concentration

Applications of Conductivity Measurement

  • Water Quality Monitoring: Assessing purity and contamination
  • Industrial Process Control: Monitoring concentration in solutions
  • Environmental Studies: Tracking pollution and salinity
  • Agriculture: Monitoring soil salinity and irrigation water quality
  • Aquaculture: Maintaining optimal water conditions
  • Laboratory Analysis: Quality control of reagents and solutions

Practical Tip: When measuring conductivity, always calibrate your instrument with standard solutions of known conductivity (typically KCl solutions). Temperature compensation is essential for accurate comparisons between measurements taken at different temperatures.

Frequently Asked Questions

Conductivity measures a solution's ability to conduct electricity, which depends on the concentration and mobility of ions. TDS (Total Dissolved Solids) estimates the total concentration of dissolved substances. TDS is typically calculated from conductivity using a conversion factor (usually 0.5-0.8), as conductivity provides a good approximation of ion concentration.

Temperature affects conductivity in two main ways: 1) Increased temperature reduces the viscosity of water, allowing ions to move more freely, and 2) Higher temperatures increase the kinetic energy of ions, enhancing their mobility. Conductivity typically increases by about 2% per °C rise in temperature, which is why measurements are usually standardized to 25°C.

The cell constant (K) is a characteristic of a conductivity cell that relates the measured resistance to conductivity. It is defined as the distance between electrodes divided by their area (K = d/A). Different cell constants are used for different conductivity ranges: low constants (0.1 cm⁻¹) for high conductivity solutions, and high constants (10 cm⁻¹) for low conductivity solutions. Using the correct cell constant is essential for accurate measurements.

TDS estimation from conductivity is reasonably accurate for many practical purposes, typically within 10-20% of actual TDS. The accuracy depends on using an appropriate conversion factor for the specific ionic composition of the solution. For natural waters with mixed salts, a factor of 0.65 is commonly used. For solutions dominated by a single salt (like NaCl), the factor can be more precise (0.55-0.75 depending on the salt).

Conductivity primarily measures ionic contaminants. Non-ionic substances (like sugars, alcohols, or organic solvents) do not significantly affect conductivity unless they dissociate into ions. For comprehensive water quality assessment, conductivity should be used alongside other parameters like pH, turbidity, and specific chemical tests for non-ionic contaminants.