Estimate seawater density from temperature and salinity accurately. Review formulas, charts, tables, and exportable results. Make faster ocean property decisions with cleaner numeric confidence.
Use the grid below. Large screens show three columns, smaller screens show two, and phones show one.
After calculation, the chart shows density against temperature at the chosen salinity.
This calculator uses the common seawater density polynomial for salinity S in PSU and temperature T in °C at atmospheric pressure:
ρ(S,T) = ρw(T) + A(T)S + B(T)S3/2 + C·S²
Where:
ρw(T) = 999.842594 + 6.793952×10⁻²T − 9.095290×10⁻³T² + 1.001685×10⁻⁴T³ − 1.120083×10⁻⁶T⁴ + 6.536332×10⁻⁹T⁵A(T) = 0.824493 − 4.0899×10⁻³T + 7.6438×10⁻⁵T² − 8.2467×10⁻⁷T³ + 5.3875×10⁻⁹T⁴B(T) = −5.72466×10⁻³ + 1.0227×10⁻⁴T − 1.6546×10⁻⁶T²C = 4.8314×10⁻⁴The page also reports sigma-t, which is simply ρ − 1000 in kg/m³.
| Temperature (°C) | Salinity (PSU) | Density (kg/m³) | Sigma-t |
|---|---|---|---|
| 0 | 35 | 1,028.106 | 28.106 |
| 10 | 35 | 1,026.952 | 26.952 |
| 20 | 35 | 1,024.763 | 24.763 |
| 25 | 35 | 1,023.343 | 23.343 |
| 5 | 40 | 1,031.645 | 31.645 |
You can enter temperature in °C, °F, or K. Salinity can be entered as PSU or ppt. Density can be shown in kg/m³, g/cm³, or lb/ft³.
For practical use on this page, PSU and ppt are treated as numerically similar. That matches many everyday seawater calculations, though strict laboratory contexts may distinguish measurement methods.
No. This version estimates density from temperature and salinity at atmospheric pressure. Deep-ocean work should use a full equation of state that includes pressure explicitly.
Warmer water expands, so the same mass occupies more volume. That volume increase lowers density when salinity and pressure remain unchanged.
Dissolved salts add mass to water and change intermolecular structure. In most practical seawater conditions, that makes denser water than freshwater at the same temperature.
Sigma-t is seawater density minus 1000 kg/m³. Oceanographers use it because it gives a compact way to compare density changes across typical marine conditions.
Yes, for many introductory and intermediate problems. It is especially useful for comparing trends, checking examples, and building intuition about temperature-salinity effects on seawater density.
Yes. After calculating, use the CSV and PDF buttons in the result section. They save the current inputs, main outputs, and chart-related range details.
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.