Hydrostatic Pressure Calculator
Find fluid pressure at a given depth.
Defaults to Earth's 9.81 m/s² if left blank.
Results update as you type.
How it works
Hydrostatic pressure is the pressure exerted by a fluid at rest due to the weight of the fluid above a given point, and this hydrostatic pressure calculator returns it from the fluid's density, the depth, and gravity. The deeper you go, the more fluid sits overhead, so the pressure climbs steadily with depth. This is why your ears pop at the bottom of a swimming pool and why submarines must be built to withstand crushing loads far below the surface. This calculation matters across engineering, diving, and earth science. Dam walls are thicker at the base because pressure is greatest there, divers track pressure to manage their air and avoid injury, and tank designers use it to size walls that will not rupture. A hydrostatic pressure calculator makes these estimates quick, letting you compare fluids and depths without wrestling the formula by hand each time. The formula works because pressure at depth equals the weight of the column of fluid pressing on each unit of area, which grows with density, gravity, and depth. Note that this gives the pressure due to the fluid alone; to find absolute pressure you add atmospheric pressure at the surface. Students, engineers, and divers all rely on a hydrostatic pressure calculator to predict how fluids push on the structures and bodies immersed in them.
P = density × gravity × depth
Hydrostatic pressure is the weight of the fluid column pressing down on a point, so multiplying fluid density by gravitational acceleration by depth gives the force per unit area at that depth. The formula works because a taller column of fluid contains more mass above the point, and a denser fluid packs more mass into the same height, both of which increase the downward force. Gravity converts that stacked mass into weight, and dividing by area is already built into using density, yielding pressure directly in pascals.
Source:Standard physics (Pascal's principle)
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter fluid density and depth.
- 2
Adjust the options
Adjust gravity if they apply — sensible defaults are already set.
- 3
Read your result
Hydrostatic pressure updates instantly as you type — no button to press.
Frequently asked questions
Does this include atmospheric pressure?
No. This calculator returns the gauge pressure caused by the fluid column alone, not the absolute pressure. To find absolute pressure at that depth, add the atmospheric pressure acting on the fluid surface, roughly 101,325 pascals at sea level. Gauge pressure is what most engineering and diving calculations use because it represents the pressure above the surrounding atmosphere, which is the load a submerged structure actually experiences.
What density should I use for water?
Fresh water has a density of about 1,000 kilograms per cubic metre, while seawater is denser at roughly 1,025 kilograms per cubic metre because of dissolved salts. Using the correct value matters for accuracy, since denser fluid produces higher pressure at the same depth. For other liquids, look up their density: mercury, for example, is about 13,600 kilograms per cubic metre and produces far greater pressure.
Why does pressure not depend on the container's shape?
Hydrostatic pressure depends only on depth, density, and gravity, not on the width or shape of the container. This is known as the hydrostatic paradox: a narrow tube and a wide tank filled to the same depth exert the same pressure at the bottom. Pressure results from the height of the fluid column above a point, so only vertical depth matters, not how much total fluid surrounds it.
How much does pressure increase per metre of water?
In fresh water, pressure rises by about 9,810 pascals for every metre of depth, which is close to one-tenth of an atmosphere per metre. This means that at ten metres deep, the fluid adds roughly one full atmosphere of pressure on top of the air pressure at the surface. Divers use this rule of thumb constantly to gauge the loads their bodies and equipment face.
Can I use this for gases or only liquids?
The formula assumes constant density, which works well for liquids because they barely compress. Gases compress significantly under their own weight, so their density changes with height and this simple formula becomes inaccurate over large vertical distances. For thin gas layers or small depth changes it gives a reasonable approximation, but atmospheric pressure over kilometres requires a more complex model that accounts for varying density.