🔬 Hydrostatic Pressure Calculator
Calculate the pressure exerted by a fluid at rest using the fundamental formula P = ρgh. Enter fluid density, depth, and gravitational acceleration to find both gauge and absolute pressure. Supports multiple units and includes common fluid density references.
What Is Hydrostatic Pressure?
Hydrostatic pressure is the pressure exerted by a fluid at rest due to the force of gravity. It increases linearly with depth and depends on the fluid's density and the gravitational acceleration. The fundamental equation is:
P = ρ · g · h
where P = pressure (Pa), ρ = fluid density (kg/m³), g = gravitational acceleration (m/s²), h = depth (m)
Hydrostatic pressure has several important characteristics:
- Acts equally in all directions — at a given point, pressure is the same in every direction.
- Depends only on depth — not on the shape or volume of the container (hydrostatic paradox).
- Increases linearly with depth — each additional meter of depth adds ρ·g to the pressure.
- Independent of the container's shape — the pressure at the bottom of a narrow tube is the same as in a wide tank at the same depth.
Gauge Pressure vs Absolute Pressure
There are two ways to measure pressure:
- Gauge Pressure — pressure measured relative to atmospheric pressure (Pgauge = ρgh).
- Absolute Pressure — pressure measured relative to a perfect vacuum (Pabsolute = P₀ + ρgh).
At sea level, atmospheric pressure is approximately 101,325 Pa (1 atm). Gauge pressure is what most pressure gauges display, while absolute pressure is used in thermodynamics and gas laws.
Why Use This Calculator?
- Instant results: Get gauge and absolute pressure in multiple units.
- Step-by-step breakdown: See exactly how the conversion is calculated.
- Unit flexibility: Enter density and depth in your preferred units.
- Free & private: No registration, no data storage — all calculations are done in your browser.
❓ Hydrostatic Pressure Calculator FAQ
What is the formula for hydrostatic pressure?
The formula is P = ρgh, where ρ is fluid density, g is gravitational acceleration, and h is the depth below the fluid surface.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to atmospheric pressure (Pgauge = ρgh). Absolute pressure includes atmospheric pressure (Pabsolute = P₀ + ρgh).
How much pressure does 10 meters of water add?
Freshwater has a density of 1000 kg/m³, so 10 meters of water adds approximately 98.1 kPa, which is nearly 1 atmosphere (101.325 kPa).
What is the standard value for gravity?
The standard value for gravity is 9.80665 m/s². For most calculations, 9.81 m/s² is sufficient.
What is the density of freshwater?
Freshwater has a density of approximately 1000 kg/m³ (1 g/cm³) at 4°C.
What is the density of seawater?
Seawater has a density of approximately 1025 kg/m³, which varies with temperature and salinity.
Does the shape of the container affect hydrostatic pressure?
No. This is known as the hydrostatic paradox. Pressure at a given depth depends only on the fluid density and depth, not on the container's shape.
How accurate is this calculator?
This calculator uses the exact hydrostatic pressure formula P = ρgh. Accuracy depends on the precision of the input values. You can adjust the decimal precision in the output.
Is this calculator free?
Yes, this calculator is completely free to use. No registration or personal data storage is required.
What units does this calculator support?
Density: kg/m³, g/cm³, lb/ft³. Depth: meters, centimeters, millimeters, feet, inches. Pressure is displayed in Pa, kPa, bar, PSI, and atm.