Density of Seawater
Seawater is about 2.5 percent denser than fresh water, and that small difference runs through offshore drilling, coastal groundwater, and every marine pressure calculation.
1,025 kg per cubic meter, 8.55 ppg
| Typical open ocean density | 1,025 kg per cubic meter |
| In ppg | 8.55 ppg |
| In pounds per cubic foot | 64.0 lb/ft³ |
| Pressure gradient | 0.445 psi per foot |
| Salinity basis | about 35 grams of salt per kilogram |
Notes for design and site
The 40 kilograms of dissolved salt in each cubic meter is exactly what the Ghyben Herzberg relation leverages into forty meters of interface movement per meter of water table change. Offshore, riser and seawater hydrostatics use 0.445 psi per foot, and cold, salty, deep water runs slightly denser than the surface number.
Related Calculators and Reference
- Mud Weight and Pressure Gradient Calculator: convert these densities into downhole pressures.
- Equivalent Circulating Density: what the formation feels while pumping.
- American Petroleum Institute: source of drilling fluid specifications.