Convert PSU, g/kg, mg/L, ppm, and related salinity measurements for oceanography, aquariums, drinking water checks, and environmental monitoring. Fast results, no sign-up, and no manual lookup table.
Scientific and technical measurements
Specialized and historical measurements
Salinity and TDS values appear in different forms depending on whether you work in marine science, aquaculture, aquarium maintenance, or water treatment. This page helps translate between the labels used by lab reports, meters, field manuals, and consumer devices.
If you need adjacent chemistry tools, use the Concentration Converter, Electric Conductivity Converter, and pH Converter for related water-quality workflows.
For many practical conversions, the main approximation is:1 PSU ≈ 1 g/kg ≈ 1000 mg/L ≈ 1000 ppm
This works well for quick mass-based comparisons, especially when water density is close to 1 g/mL. Conductivity-based salinity calculations are more nuanced and depend on temperature, sample chemistry, and calibration method.
Treat aquarium, seawater, and potable-water conversions as context-dependent when precision matters. This tool gives a practical conversion baseline that is much faster than manual math.
Example
35 PSU = about 35,000 mg/L
Typical open-ocean salinity reference.
Example
1 g/kg = 1000 mg/L
Useful for quick mass-based comparisons.
Example
500 ppm = 500 mg/L
Common freshwater TDS interpretation.
Example
0 PSU = 0 mg/L
Idealized freshwater baseline.
Conductivity, salinity, and TDS are related but not interchangeable in a perfectly exact way. If you are calibrating instruments or documenting regulated water-quality data, confirm the instrument method, sample temperature, and conversion basis.
Salinity usually refers to the total salt content of water and is often expressed as PSU, ppt, or g/kg. TDS means total dissolved solids and is commonly reported as mg/L or ppm, especially in water-quality workflows.
A common approximation is 1 PSU ≈ 1 g/kg ≈ 1000 mg/L ≈ 1000 ppm for dilute-to-moderate salinity contexts. The converter applies the relevant relationships instantly, but conductivity-based salinity models can vary by method and temperature.
Yes. The tool is useful for aquarium, marine, and aquaculture checks when you need to compare salinity, TDS, ppt, or conductivity-style readings across devices and reference guides.
Not always. Approximate mass-based conversions are straightforward, but conductivity-derived salinity depends on temperature, calibration, and the dissolved-ion composition of the sample.
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