Density of Seawater
| Value | 1025 kg/m³ |
| Status | Measured: ± 5 kg/m³ (0.0049 relative) |
| Source | UNESCO/IOC International Equation of State of Seawater (EOS-80) |
| Categories | Material PropertiesEngineering & Tradefluids |
| kilogram per cubic meter | 1,025 kg/m³ |
| gram per cubic centimeter | 1.025 g/cm³ |
| gram per milliliter | 1.025 g/mL |
| kilogram per liter | 1.025 kg/L |
| pound per cubic foot | 63.98866 lb/ft³ |
| pound per US gallon | 8.5540396 lb/gal |
Learning zone
Standard seawater carries roughly 35 grams of dissolved salt per kilogram, which adds about 2.7 % to the density of fresh water. Naval architects use 64 lb/ft³ for salt water against 62.4 lb/ft³ for fresh — the difference is why a ship rides visibly higher leaving a river for the sea, and why load lines are marked separately for fresh and salt water.
The real ocean is not one number. Surface density runs from about 1021 kg/m³ in warm, rain-diluted tropical water to 1028 kg/m³ in cold polar water, and the Baltic is nearer 1005 kg/m³. Density also climbs with depth: pressure alone adds about 0.5 % per kilometre. Treat 1025 kg/m³ as a design figure for intakes, hull displacement and hydrostatic head, and use measured salinity and temperature whenever the answer matters — density-driven circulation and stratification live entirely inside the digits this value throws away.