How to Convert Specific Conductivity to Salinity

The word "specific," when used in physics and chemistry, has a (specific) meaning. It refers to a quantity divided by an extensive (dimensional) measure to make it a measure of a substance's properties instead of peculiar to a particular object. For example, specific conductivity (or just conductivity, which by definition already is a specific measure) measures a substance's ability to conduct electricity. Scientists measure conductivity in seawater to determine salinity. While the conversion from the former to the latter uses a long equation of several terms, you can use an online calculator to make the conversion with just three variables.

Instructions

1. Convert your conductivity measurement's unit from siemens per meter (S/m) to milli-siemens per centimeter (mS/cm). In other words, multiply by 10.

2. Raise the conductivity (in mS/cm) to the power 1.0878.

3. Multiply the result by 0.4665. This gives you salinity in grams (of salt) per liter (of solution).

Tips & Warnings

• An accurate conversion for salinity ranges 5 to 100 milli-siemens per centimeter, or 0.5 to 10 S/m. This is useful for aquariums, freshwater and saltwater. The above parameters apply to 25 degrees Celsius.

References

• Marine Freshwater Research
• Seabird

Resources

• UNESCO: Algorithms for Computation of Fundamental Properties of Seawater
• Johns Hopkins Applied Physics Lab: A Seawater Equation of State Calculator
• Envco Global: Conductivity-Salinity Table