Calculate pure freshwater and ocean seawater density based on temperature (-5°C to 100°C) and salinity (0 to 40 PSU).
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The Water Density Calculator computes the exact density of liquid water across varying temperatures (from sub-zero supercooled water to boiling) and salinities (from distilled freshwater to dense ocean water). It implements standard UNESCO and Kell equation of state formulations.
\rho(T, S) = \rho_{\text{fresh}}(T) + S \cdot \left(0.8245 - 4.09 \times 10^{-3} T + 7.64 \times 10^{-5} T^2\right)Water exhibits an anomalous density maximum at 3.98°C (999.97 kg/m³). Adding dissolved salts increases density linearly with salinity.
Scenario: Measuring Atlantic seawater at 20°C with standard 35 PSU salinity.
Freshwater density at 20°C: ~998.20 kg/m³.
Salinity addition for 35 PSU at 20°C: +26.55 kg/m³.
Total Seawater Density: 998.20 + 26.55 = 1,024.75 kg/m³.
When water freezes into crystalline ice, hydrogen bonding creates an open hexagonal lattice structure that expands volume by ~9%, lowering ice density to ~917 kg/m³, making it buoyant.
At 20°C (68°F), pure water has a density of 998.2 kg/m³ (0.9982 g/cm³ or ~62.31 lbs/ft³).
PSU stands for Practical Salinity Unit, which is based on electrical conductivity ratios relative to a standard KCl solution. Ocean seawater averages 35 PSU (~3.5% salt by weight).
The Dead Sea has an extreme mineral salinity of approximately 340 PSU (over 30% dissolved salts), giving it a density of roughly 1,240 kg/m³, allowing people to float effortlessly.
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