Salinity Conductivity Calculator

Measure conductivity, compensate temperature, and estimate salinity precisely. Review ratios, reference values, and export summaries. Clean visuals make lab checks faster, clearer, and dependable.

Enter Sample Data

Use the full calculator below to convert conductivity to salinity or reverse the process for a target salinity at a defined temperature and pressure.

Enter the observed conductivity in the selected unit.
Use practical salinity notation. Surface seawater is often near 35.
Temperature strongly affects conductivity and the final estimate.
Use 0 dbar for most bench or surface measurements.
Used to estimate conductivity normalized to 25 °C.

Example Data Table

These example readings are illustrative. They help compare typical conductivity ranges with their estimated practical salinity.

Sample Conductivity Temperature Pressure Estimated Salinity Water Type
River Sample 0.80 mS/cm 25.0 °C 0.0 dbar 0.392 PSU Fresh Water
Brackish Canal 8.50 mS/cm 25.0 °C 0.0 dbar 4.726 PSU Brackish Water
Estuary Blend 24.00 mS/cm 20.0 °C 0.0 dbar 16.288 PSU Brackish Water
Coastal Seawater 53.00 mS/cm 25.0 °C 0.0 dbar 34.952 PSU Marine Water
Concentrated Brine 70.00 mS/cm 25.0 °C 0.0 dbar 47.930 PSU Hypersaline Water

Formula Used

This calculator uses the Practical Salinity Scale style approach with temperature and pressure corrections. It also estimates EC at 25 °C using a linear compensation factor.

1) Conductivity ratio
R = C / 42.914
where C is conductivity in mS/cm and 42.914 mS/cm is the standard reference conductivity.
2) Pressure correction
Rp = 1 + [P × (e1 + e2P + e3P²)] / [1 + d1T + d2T² + (d3 + d4T)R]
This adjusts the conductivity ratio for non-zero pressure.
3) Reduced conductivity ratio
Rt = R / [Rp × rt35(T)]
with rt35(T) represented by the standard temperature polynomial.
4) Practical salinity
S = Σ(ai × Rt^(i/2)) + [(T - 15) / (1 + k(T - 15))] × Σ(bi × Rt^(i/2))
The calculator evaluates the full polynomial terms internally.
5) Conductivity compensated to 25 °C
EC25 = C / [1 + α(T - 25)]
This is a practical linear normalization often used in field screening and water quality summaries.

The inverse mode solves for conductivity by repeatedly testing conductivity values until the target salinity is matched closely.

How to Use This Calculator

Step 1: Choose the calculation mode. Use conductivity-to-salinity for measured EC data, or salinity-to-conductivity when designing a target condition.
Step 2: Select the conductivity unit that matches your instrument or reporting format. The calculator converts everything internally to mS/cm.
Step 3: Enter temperature and pressure carefully. Even when conductivity stays the same, salinity estimates shift with environmental conditions.
Step 4: Click calculate. Review the result cards, graph, and export buttons for reporting, comparison, or lab notes.

Frequently Asked Questions

1) What does this calculator estimate?

It estimates practical salinity from conductivity, temperature, and pressure, or finds conductivity for a target salinity. It also shows ratio values, compensated EC at 25 °C, charting, and export-ready summaries.

2) Is salinity really measured in PSU?

Practical salinity is technically dimensionless. Many labs still write PSU for convenience. This page follows that common convention to make the output easier to read while keeping the calculation based on the practical salinity scale.

3) Why is temperature required?

Conductivity changes strongly with temperature. The same dissolved salt content can produce different conductivity readings at different temperatures, so compensation is necessary before estimating salinity accurately.

4) Do I need pressure for surface samples?

Usually no. For bench testing, tanks, rivers, and near-surface seawater, pressure can often be left at 0 dbar. Deeper marine work benefits more from pressure correction.

5) Which conductivity units are supported?

The form supports µS/cm, mS/cm, dS/m, and S/m. Internally, all values are converted to mS/cm so the same equation set can be applied consistently.

6) Is the 25 °C conductivity exact?

It is an engineering estimate using a linear temperature coefficient. That makes it useful for field screening, quick comparisons, and reporting, but specialized instruments may apply more advanced compensation models.

7) Does this work well for freshwater?

It can provide a screening estimate, but the practical salinity scale is most reliable for typical saline waters. Very low salinity freshwater results should be interpreted carefully and compared with laboratory methods when precision matters.

8) Why include CSV and PDF downloads?

They make it easier to archive a result, share it with colleagues, attach it to a lab record, or reuse it in later reports without retyping the values manually.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.