Solution Conductivity Calculator

Calculator

Input type

Choose what you measured directly.

Resistance

Conductance is computed as 1/R.

Cell constant (Kcell)

cm⁻¹

Accounts for electrode geometry and spacing.

Temperature

°C

Measured solution temperature.

Reference temperature

°C

Common reference is 25 °C.

Temperature coefficient (α)

%/°C

Typical aqueous range: 1.5–2.5 %/°C.

Concentration (optional)

mol/L

Used to compute molar conductivity.

TDS factor

mg/L per µS/cm

Common factors: 0.50 (NaCl) to 0.70 (442).

Output conductivity unit

All calculations run internally in S/cm.

Reset

Example data table

Sample	Kcell (cm⁻¹)	T (°C)	α (%/°C)	Resistance (Ω)	TDS factor	Concentration (mol/L)
Sample A	1.00	25.0	2.00	520	0.50	0.0010
Sample B	0.90	30.0	2.10	980	0.55	0.0020
Sample C	1.10	20.0	1.90	2100	0.50	0.0100

Tip: Use the calculator above to reproduce and export computed outputs.

Formula used

1) Conductance from resistance

G = 1 / R

R is resistance (Ω). G is conductance (S).

2) Conductivity from conductance and cell constant

κ = G × Kcell

Kcell is in cm⁻¹, so κ is in S/cm.

3) Temperature correction to a reference temperature

κref = κT / ( 1 + α (T − Tref) )

α is the temperature coefficient in 1/°C (entered here as %/°C).

4) Molar conductivity (optional)

Λm = (1000 × κref) / c

c is concentration in mol/L. Output is S·cm²/mol.

5) Total dissolved solids estimate

TDS (mg/L) = κ (µS/cm) × factor

This is an empirical estimate and depends on composition.

How to use this calculator

Select whether you measured resistance or conductance.
Enter the value and choose the correct unit.
Provide the cell constant from calibration data.
Enter solution temperature and reference temperature.
Set α and TDS factor appropriate for your solution.
Click Calculate, then export results as CSV or PDF.

Conductivity as a quality control signal

Conductivity (κ) tracks ionic strength and is often used as a fast acceptance test for buffers, wash solutions, and process water. In routine checks, a stable κ at 25 °C supports consistent salt dosing. Deviations can indicate dilution error, evaporation, or contamination. As a practical baseline, ultrapure water may read in the low single-digit µS/cm range, while common saline mixtures move into mS/cm territory.

Why the cell constant matters

The electrode geometry is captured by the cell constant Kcell (cm⁻¹). A probe with Kcell near 1.0 is typical for general aqueous work. If Kcell is off by 5%, κ will also be off by 5% because κ = G × Kcell. This calculator keeps Kcell explicit so you can enter the value obtained from calibration against standards, which improves comparability across instruments and sites.

Temperature correction supports trending

Most aqueous solutions show κ increasing with temperature. To trend results, labs often normalize to 25 °C using a temperature coefficient α (commonly 1.5–2.5% per °C). The correction implemented here is κref = κT / (1 + α(T − Tref)). Using the same α and Tref across batches reduces false alarms when room temperature shifts between morning and afternoon runs.

Unit discipline reduces reporting mistakes

Conductivity is reported as µS/cm, mS/cm, S/cm, or S/m depending on context. This tool computes internally in S/cm and converts on output so that exported results stay consistent. Remember that 1 S/cm equals 100 S/m. Selecting the output unit to match your SOP prevents unit conversions from being repeated in spreadsheets and reduces transcription errors.

Molar conductivity adds concentration insight

When concentration (mol/L) is provided, the calculator reports molar conductivity Λm in S·cm²/mol using Λm = (1000 × κref) / c. Λm helps compare electrolytes across different dilutions. In dilute regimes, Λm often rises as ion–ion interactions weaken. Reporting Λm alongside κ can separate “stronger solution” effects from “higher mobility” effects in method development.

TDS estimation for field-style summaries

Some workflows prefer total dissolved solids (mg/L) as a single number. This tool estimates TDS using TDS = κ(µS/cm) × factor. Typical factors range from about 0.50 (NaCl-like) to about 0.70 (mixed-ion 442 style). Because composition controls the factor, treat TDS as an estimate for screening and complement it with gravimetric or ion chromatography when accuracy is critical.

FAQs

1) What should I enter if my meter shows “conductivity” directly?

If you already have conductivity, you can use the calculator mainly for temperature correction by converting your value to an equivalent conductance and Kcell, or by using your meter’s correction. This tool is optimized for resistance or conductance inputs.

2) How do I find the correct cell constant?

Calibrate the probe with a certified conductivity standard near your expected range. The meter or procedure yields Kcell. Enter that calibrated Kcell here to keep κ proportional to your measured conductance and improve cross-day consistency.

3) What α value should I use for temperature correction?

Many aqueous solutions fall around 1.5–2.5% per °C, but α depends on ions and concentration. Use your SOP value or determine α by measuring the same sample at two temperatures and fitting the slope.

4) Why does corrected conductivity decrease when temperature increases?

The correction normalizes κ to a reference temperature. If T is higher than Tref, κT is divided by a factor greater than 1, producing a lower κref. This does not mean the solution became less conductive at the measurement temperature.

5) Is the TDS value accurate?

TDS is an empirical estimate. The factor depends on composition and can vary substantially between NaCl-like, mixed salts, and organics. Use it for screening, and verify with a method suited to your matrix when precision matters.

6) Can I export results for audit trails?

Yes. After calculation, download CSV for spreadsheets or PDF for reports. Exports include the key inputs and computed outputs shown in the Results panel, which supports traceability and review without retyping values.