Estimate seawater salinity from conductivity, temperature, and pressure quickly. Convert units instantly with clear outputs. Export your readings for reports and lab records today.
| Timestamp | Method | Inputs | T (C) | P (dbar) | Salinity (PSU) | Class | Density (kg/m3) |
|---|---|---|---|---|---|---|---|
| Example | Conductivity | C=49.5000 mS/cm | 20 | 0 | 36.2 | Seawater | 1026.6 |
| Example | Chlorinity | Cl=19.0000 g/kg | 15 | 0 | 34.32445 | Seawater | 1026.5 |
| Example | TDS | TDS=10.0000 g/L | 25 | 0 | 10 | Brackish | 1005.2 |
This calculator supports three practical routes to salinity. Choose the route that matches your instrument.
Open-ocean surface seawater commonly falls between 33 and 37 PSU, while estuaries can vary from 0.5 to 30 PSU depending on river flow and tides. In coastal lagoons and evaporation basins, hypersaline conditions above 40 PSU are frequent. Recording temperature and pressure alongside salinity improves comparability across sampling sites.
When conductivity is available, the calculator uses a conductivity ratio referenced to 42.914 mS/cm at 35 PSU and 15 °C. Typical ocean conductivity spans roughly 48 to 56 mS/cm at 20–25 °C. Higher temperatures increase measured conductivity, so applying temperature correction reduces bias when comparing warm and cold samples.
For titration-based datasets, salinity can be estimated from chlorinity using S ~ 1.80655 × Cl, where Cl is in g/kg. A chlorinity near 19.0 g/kg corresponds to about 34.3 PSU, a representative mid-ocean value. This pathway is useful for historical records and quality checks against conductivity measurements.
If only total dissolved solids are reported, the calculator treats TDS in g/L as an approximate g/kg salinity near seawater density. For example, 10 g/L indicates brackish water, while 35 g/L indicates seawater. Use this option for field screening, not for high-precision oceanographic analysis.
The output labels fresh, brackish, seawater, and hypersaline to support quick decisions, such as corrosion risk or aquaculture suitability. A simple density estimate is included to contextualize stratification; density typically increases with salinity and decreases with temperature.
Use the saved table to build a traceable sampling record with timestamps and method notes. Export CSV for laboratory information systems and PDF for attachments to reports. For best practice, document instrument calibration, rinse procedure, and sample handling time to reduce contamination and drift. The Plotly chart visualizes your recent results so outliers are obvious. Compare multiple depths to spot haloclines, and compare repeat runs to quantify instrument drift. A stable seawater reference should reproduce within about 0.1 PSU for routine work. If differences grow, clean the cell, recheck temperature compensation, and rerun a standard. Keep units consistent when copying values from meters or lab reports. Store raw readings to support audits and later recalculation.
PSU is a practical salinity unit derived from conductivity ratios, while ppt is a mass-based “parts per thousand” style label. In routine seawater work they are often reported similarly, but they are not strictly identical definitions.
If you have a calibrated conductivity meter and stable temperature, the conductivity method is typically the best choice. Use chlorinity for legacy titration datasets, and use TDS only for quick screening or approximate comparisons.
Conductivity increases with temperature even if salt content is unchanged. Correcting for temperature helps compare samples taken at different conditions, such as surface versus deeper water, or winter versus summer sampling campaigns.
Enter the pressure you record for the sample, typically in dbar for oceanographic logs. This calculator stores pressure for documentation; advanced pressure corrections are simplified, so treat it as metadata for reports.
The density is a quick contextual estimate to help interpret stratification trends. It is not a replacement for full seawater equation-of-state calculations and should not be used for engineering design or safety-critical decisions.
Outliers often indicate a unit mismatch, poor temperature stabilization, trapped air bubbles in the conductivity cell, or drift from incomplete cleaning. Recheck units, rerun a standard, and repeat the measurement to confirm.
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.