Hydrostatic Pressure Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
Hydrostatic pressure is calculated with P = ρ × g × h, where ρ is the fluid density, g is the acceleration of gravity (9.81 m/s²), and h is the depth. At 10 m under fresh water, the hydrostatic pressure is about 98.1 kPa.
Explanation
Hydrostatic pressure is the pressure exerted by the weight of a fluid at rest at a given depth, not counting the atmospheric pressure that adds on at the surface. It increases linearly with depth: the deeper you go into a fluid, the greater the weight of the fluid column above pressing on each point. This calculator gives the relative pressure due to the fluid alone (often called gauge pressure); to get the absolute pressure (the one actually experienced by a diver, for example), you need to add the atmospheric pressure at the surface, about 101.3 kPa at sea level. Fluid density changes the result proportionally: seawater, denser than fresh water due to dissolved salt (about 1,025 kg/m³ versus 1,000 kg/m³), exerts slightly higher pressure at the same depth. For the density of a material or liquid, see our density calculator.
Example: fresh water at 10 m depth
Inputs
Density: 1,000 kg/m³ (fresh water). Depth: 10 m.
Calculation
Pressure = 1,000 × 9.81 × 10 = 98,100 Pa, or 98.1 kPa.
Result
The hydrostatic pressure at this depth is 98.1 kPa.
Frequently asked questions
What's the difference between hydrostatic pressure and absolute pressure?
The hydrostatic pressure calculated here measures only the contribution from the fluid's weight. Absolute pressure, the one actually experienced at this depth, is obtained by adding the surface atmospheric pressure (about 101.3 kPa at sea level) to this result — an important distinction in diving, where it's absolute pressure that matters for physiology.
Why doesn't the shape of the container matter in this calculation?
This is a remarkable property of hydrostatic pressure: it depends only on depth and fluid density, never on the shape or volume of the container (a principle sometimes called the hydrostatic paradox). Two points at the same depth in the same fluid experience exactly the same pressure, whether the container is wide or narrow.
Does this calculator work for a gas rather than a liquid?
The formula remains valid in principle, but it's mainly accurate for liquids, treated as incompressible (constant density with depth). For a gas, density itself varies with pressure and altitude, which makes this simplified calculation less suited over large height differences.