Fluid Pressure
Each particle of a liquid is subjected to a gravitational force directed toward the Earth. The deeper we are, the more such particles are above us, and the higher the fluid pressure (because the acting force is greater). If the fluid is at rest, we call it hydrostatic pressure.
An interesting fact is that the value of hydrostatic pressure does not depend on the size and shape of the tank — only on the depth. Surprisingly, the same hydrostatic pressure will be present in a huge pool as in a thin pipe, provided they have the same height.
Hydrostatic Pressure Equation
Our hydrostatic pressure calculator uses the following hydrostatic pressure formula:
p = ρ × g × h + p₀
Where:
- p — Hydrostatic pressure
- ρ (rho) — Density of the fluid
- g — Gravitational acceleration (average Earth value: g = 9.80665 m/s²)
- h — Depth below the fluid surface
- p₀ — External (atmospheric) pressure (default: p₀ = 1 atm = 101,325 Pa)
The formula for hydrostatic pressure also determines the buoyancy force, first described by Archimedes. You can expand the Additional parameters section in our calculator to change the gravitational acceleration g and the external pressure p₀.
Measurement Systems
The calculator supports two measurement systems:
- Metric (SI) — depth in meters (m), density in kg/m³, pressure in Pa / kPa / bar / atm / MPa
- American (Imperial) — depth in feet (ft), density in lb/ft³, pressure in psi / psf / atm
Results are always shown in both systems simultaneously so you can compare them easily.
The Deepest Place on Earth
The deepest part of the world's oceans is the Mariana Trench, located in the Pacific Ocean. It reaches the highest known depth of around 11,000 m (36,089 ft). Using our hydrostatic pressure calculator with seawater (ρ = 1,025 kg/m³) at that depth:
- Gauge pressure ≈ 110,650 kPa ≈ 1,091 atm
- Total pressure (with atmosphere) ≈ 110,751 kPa ≈ 1,092 atm
The pressure at the bottom of the Mariana Trench is more than 1,000 times greater than atmospheric pressure at sea level!
How to Use the Hydrostatic Pressure Calculator
- Select the measurement system — Metric (m, kg/m³) or American (ft, lb/ft³).
- Choose the fluid — select from the dropdown (fresh water, salt water, mercury, oil, blood, etc.) or choose "Custom" to enter your own density.
- Enter the depth — the depth at which you want to calculate hydrostatic pressure.
- Click Calculate — the hydrostatic pressure is calculated instantly and shown in Pa, kPa, bar, atm, psi, and MPa.
- Optional — Advanced parameters: expand to adjust gravitational acceleration (g) or external (atmospheric) pressure (p₀).
Fluid Density Presets
| Fluid | Density (kg/m³) | Density (lb/ft³) |
|---|---|---|
| Fresh Water | 997 | 62.24 |
| Salt Water | 1,022 | 63.80 |
| Seawater | 1,025 | 64.00 |
| Oil (crude) | 870 | 54.31 |
| Mercury | 13,600 | 848.99 |
| Milk | 1,030 | 64.31 |
| Blood | 1,060 | 66.19 |
| Gasoline | 700 | 43.71 |
| Glycerin | 1,261 | 78.74 |
| Honey | 1,420 | 88.68 |
FAQs
What is hydrostatic pressure?
Hydrostatic pressure is the pressure generated by a fluid at rest due to the Earth's gravitational pull. For a fish, the entire column of water above it plus the atmospheric pressure generates the hydrostatic pressure acting on it.
Does the shape of the container affect hydrostatic pressure?
No. Hydrostatic pressure depends only on the depth of the fluid, its density, and gravitational acceleration — not on the shape or volume of the container (Pascal's paradox).
What is gauge pressure vs total pressure?
Gauge pressure (ρgh) is the pressure due to the weight of the fluid column alone, without atmospheric pressure. Total pressure (ρgh + p₀) includes atmospheric pressure acting on the fluid surface. Our calculator shows both.
How does gravity affect hydrostatic pressure?
On planets with weaker gravity, hydrostatic pressure at the same depth is lower. On the Moon (g ≈ 1.62 m/s²) the pressure at 10 m depth in water would be about 6 times lower than on Earth. You can adjust g in the "Additional parameters" section.