Hydrostatic Pressure Calculator
This hydrostatic pressure calculator finds the pressure at a depth in a fluid using P = ρ g h. Enter the depth, the fluid density, and gravity, and the hydrostatic pressure calculator returns gauge pressure in kPa, bar, and psi, plus absolute pressure. It covers water tanks, dams, diving, and any hydrostatic head calculation.
Results
The Hydrostatic Pressure Calculator is part of our Fluids collection. Browse more fluids to size, convert, and check your work alongside this tool.
What the hydrostatic pressure calculator shows
The deeper you go in a fluid, the more fluid presses down from above. The hydrostatic pressure calculator turns depth into pressure using the weight of that fluid column. It reports gauge pressure, which is pressure above the atmosphere, and absolute pressure, which adds the atmosphere on top.
Hydrostatic calculation formula
The hydrostatic calculation is:
ρ is the fluid density, g gravity, and h the depth below the surface. Pressure rises in a straight line with depth: in fresh water it grows by about 9.81 kPa, or roughly 1.42 psi, for every metre.
Calculate hydrostatic pressure in psi: example
Fresh water 10 m deep. The hydrostatic pressure calculator gives:
Absolute pressure is 98.1 + 101.3 = 199.4 kPa, about two atmospheres. That is why divers feel the pressure double at 10 m.
How to use the hydrostatic pressure calculator
Enter the depth in metres, the fluid density, and gravity. Use 1,000 kg/m³ for fresh water and about 1,025 kg/m³ for sea water. The hydrostatic pressure calculator returns the gauge pressure in kPa, bar, and psi, and the absolute pressure in kPa. Shape and width of the container do not matter, only the vertical depth.
Reading the hydrostatic head pressure calculator result
Gauge pressure is what a pressure gauge reads and what a tank wall or pipe must resist from the fluid. Absolute pressure matters for gas behaviour, such as air in a diver's lungs. The hydrostatic head pressure calculator gives the static pressure only; flowing fluids also have velocity pressure and friction losses.
When to use the hydrostatic head calculation
- Designing tank walls with a hydrostatic head calculation
- Finding water pressure from a header tank height
- Understanding pressure at diving depths
- Converting a tank level reading into pressure
Common hydrostatic pressure calculator mistakes
- Using pipe length. Use vertical depth only.
- Mixing gauge and absolute. State which one you need.
- Wrong density. Sea water and oils differ from fresh water.
Tips for accurate results
- Measure depth vertically from the free surface.
- Use the fluid's density at its working temperature.
- Add a safety factor when sizing tank walls.
Hydrostatic level measurement calculation
Many tank level sensors are pressure sensors at the bottom of the tank. A hydrostatic level measurement calculation reverses the formula: h = P ÷ (ρ g). A reading of 49 kPa in water means the level is about 5 m above the sensor. Combine that level with the tank shape in the tank volume calculator to get the volume of liquid inside.
Hydrostatic pressure calculator vs wall force
Pressure is force per unit area at one depth. The total force on a wall or gate adds up the pressure over its whole area, and because pressure grows with depth, that force acts lower than halfway down. This calculator gives the pressure at a point; total wall force is a separate calculation.
Hydrostatic pressure calculator reference (fresh water)
| Depth | Gauge kPa | Gauge psi | Absolute kPa |
|---|---|---|---|
| 1 m | 9.81 | 1.42 | 111.1 |
| 5 m | 49.1 | 7.11 | 150.4 |
| 10 m | 98.1 | 14.2 | 199.4 |
| 30 m | 294.3 | 42.7 | 395.6 |
Hydrostatic Pressure Calculator FAQ
What is the hydrostatic pressure formula?
P = ρ g h: fluid density times gravity times depth.
Does the container shape change the pressure?
No. Hydrostatic pressure depends only on depth and fluid density, not on width or shape.
What is the difference between gauge and absolute pressure?
Gauge pressure is above atmospheric; absolute adds atmospheric pressure, about 101.3 kPa at sea level.
How much does water pressure rise per metre?
About 9.81 kPa, or 1.42 psi, per metre of fresh water.