Seawater calculator
Every thermodynamic property of seawater, from the TEOS-10 Gibbs function. Density is 1/gP here, not a fitted polynomial — so sound speed, heat capacity, entropy and the expansion coefficients are all consistent with each other and with density by construction, rather than to within a fit's residual.
Under testing. This calculator is new and still being checked against use. It is provided as-is, with no warranty of any kind, and is used at your own risk. Where it disagrees with the GSW reference toolbox, GSW is the authority.
Summary
- Absolute Salinity
- 35.1650g/kg
- Conservative Temperature
- 9.8690°C
- In-situ density
- 1031.43276kg/m³
- σ₀
- 26.97469kg/m³
- Sound speed
- 1506.1361m/s
All 51 properties
Salinity
- Practical Salinity
- 35.0000
- Absolute Salinity
- 35.1650g/kg
- Reference Salinity
- 35.1650g/kg
- Preformed Salinity
- —g/kg
- Salinity anomaly
- —g/kg
- Conductivity
- 38.5295mS/cm
- Conductivity ratio
- 0.897831
- Chlorinity
- 19.3739g/kg
Temperature
- In-situ temperature
- 10.0000°C
- Potential temperature
- 9.8791°C
- Potential temperature (0 dbar)
- 9.8791°C
- Conservative Temperature
- 9.8690°C
- In-situ temperature (IPTS-68)
- 10.0024°C
- Freezing temperature
- -2.6833°C
- Freezing temperature (CT)
- -2.7007°C
- Temperature of maximum density
- -6.1035°C
Pressure and depth
- Sea pressure
- 1000.000dbar
- Height
- -992.117m
- Depth
- 992.117m
- Gravity at 0.0°N
- 9.782520m/s²
Density and spiciness
- In-situ density
- 1031.43276kg/m³
- Specific volume
- 9.69525×10^-4m³/kg
- σ₀
- 26.97469kg/m³
- σ₁
- 31.43276kg/m³
- σ₂
- 35.79204kg/m³
- σ₃
- 40.05475kg/m³
- σ₄
- 44.22320kg/m³
- Specific volume anomaly
- 1.29912×10^-6m³/kg
- Spiciness (0 dbar)
- 1.23543kg/m³
- Spiciness (1000 dbar)
- 1.50799kg/m³
- Spiciness (2000 dbar)
- 1.77113kg/m³
Expansion and compressibility
- Thermal expansion
- 1.84080×10^-41/K
- Haline contraction
- 7.46910×10^-4kg/g
- α / β
- 0.24646g/(kg K)
- Isentropic compressibility
- 4.27396×10^-101/Pa
- Isothermal compressibility
- 4.29743×10^-101/Pa
- Adiabatic lapse rate
- 1.27495×10^-4K/dbar
Energy, entropy and heat
- Isobaric heat capacity
- 3963.5922J/(kg K)
- cp0
- 3991.86795712J/(kg K)
- Specific entropy
- 141.68043J/(kg K)
- Specific enthalpy
- 49111.998J/kg
- Potential enthalpy
- 39395.812J/kg
- Internal energy
- 39318.510J/kg
- Gibbs energy
- 8995.18565J/kg
- Helmholtz energy
- -798.30294J/kg
- Chemical potential of water
- 6.8603J/kg
- Chemical potential of sea salt
- 60.71044J/g
- Dilution coefficient
- 73.76593J/kg
Sound and phase change
- Sound speed
- 1506.1361m/s
- Latent heat of evaporation
- 2475036.4J/kg
- Latent heat of melting
- 328033.7J/kg
Nothing here matches that.
Convert a column of measurements
Rows of salinity, temperature, pressure separated by commas, tabs or spaces, one sample per line. A header row is ignored. Two further columns are read as longitude and latitude. Units are those selected above.
SourcesTEOS-10GSW Oceanographic ToolboxGSW-CGSW function reference
What it does
Absolute Salinity needs a position
TEOS-10 differs from EOS-80 in that density depends on the composition of the salt, not only on the conductivity it carries. Rivers, biology and the deep circulation leave different oceans with different compositions, so Absolute Salinity is Reference Salinity plus an anomaly that was measured rather than derived. The anomaly reaches 0.03 g/kg in the North Pacific, or about 0.024 kg/m³ of density.
The correction is a global lookup table and needs a longitude and a latitude. With a position, the atlas is fetched once and applied. Without one, the calculator uses Reference Salinity and states which salinity it used.
Full precision means the Gibbs function
The GSW toolbox evaluates most properties from a 75-term polynomial fitted to specific volume, accurate to about a part in 106. This evaluates the Gibbs function itself — IAPWS-09 for pure water, IAPWS-08 for the salt — and takes the analytic derivatives. The freezing point additionally uses the Gibbs function of ice, IAPWS-06, since it is the temperature at which the chemical potential of water in seawater equals that of ice.
Two quantities have no exact form, and their rows say so: spiciness, which is defined as a polynomial, and the reference column the depth conversion is built on.
Where it stops
The standard is fitted over 0 to 42 g/kg, the freezing point to 40 °C, and 0 to 10,000 dbar. Outside that range the polynomials still return numbers; the calculator flags them rather than clamping them. PSS-78 is defined from 2 to 42, with the Hill et al. (1986) extension below that, which is also flagged.
Checked against the reference implementation
The coefficients are transcribed mechanically from GSW-C rather than by hand, and every function is checked against GSW at points spanning the domain. Each derivative of the Gibbs function is separately checked against a central difference of the one below it, over a few thousand states. The salinity anomaly atlas reproduces GSW's own lookup to 2×10-19.
Credits
TEOS-10 is the work of SCOR/IAPSO Working Group 127, published by IOC, SCOR and IAPSO (2010) and available at teos-10.org. The reference implementation is the Gibbs SeaWater (GSW) Oceanographic Toolbox — this page is checked against its C implementation, and its function reference is the place to look up anything named here.
The pure-water and saline Gibbs functions are IAPWS-09 and IAPWS-08, and the ice one is IAPWS-06, all released by the International Association for the Properties of Water and Steam. This page is not published or endorsed by any of them.