Sea Water Density Calculator

What affects Seawater Density?

Unlike freshwater, which has a maximum density at roughly 4°C, seawater density is a complex calculation controlled by two main variables:

• Salinity (S): Measured in Practical Salinity Units (PSU), which is roughly equivalent to parts per thousand (ppt). As you add dissolved salts to water, the mass increases while the volume stays relatively similar, leading to higher density.
• Temperature (T): As water warms, the molecules move faster and push further apart, increasing the volume and leading to lower density. Conversely, cold water is much denser and sinks.

What is Sigma-t ($\sigma_t$)? Oceanographers often use Sigma-t as a shorthand for density. It is simply the calculated density minus $1000 \, kg/m^3$. For example, a density of $1025.97 \, kg/m^3$ becomes a Sigma-t of $25.97$.