Hydrostatic pressure calculator
Pressure of a liquid column from density and depth.
Fill in the fields and the result will appear here automatically.
Find the pressure increase at vertical depth h in a static liquid of constant density: Δp=ρgh. Without a surface pressure, the output is this increase relative to the surface. A positive p₀ entered as absolute surface pressure makes p₀+Δp an absolute result. The 101,325 Pa example is one standard atmosphere, not pressure at every location and weather condition.
How it works
Formula and logic
Δp=ρ·g·h and p=p₀+Δp with g=9.80665 m/s². At h=0 only p₀ remains. Vessel shape does not enter the local static-fluid balance; equal pressure at equal depth requires the same liquid and surface pressure. Capillarity and varying density are excluded here.
Example
Ten metres of fresh water gives a column pressure of 98,066.5 Pa — almost one atmosphere.
Fields and units
- Liquid density — kg/m³
- Depth — m
- External pressure — Pa
How to use
- — Enter the density of the liquid: fresh water is 1000 kg/m³.
- — Give the depth.
- — Gauge pressure is usually relative to local atmospheric pressure; absolute pressure is relative to vacuum. With blank or zero p₀ this calculator shows only the increase ρgh relative to the surface; enter actual absolute surface pressure for the total.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- OpenStax: hydrostatics and pressure references
- Limitation
- Static liquid with constant entered density and standard g. The pressure difference is relative to the surface; positive p₀ must be absolute. This does not assess vessel strength or suitability for diving.
FAQ
Does the pressure depend on the shape of the vessel?
Δp=ρ·g·h and p=p₀+Δp with g=9.80665 m/s². At h=0 only p₀ remains. Vessel shape does not enter the local static-fluid balance; equal pressure at equal depth requires the same liquid and surface pressure. Capillarity and varying density are excluded here.
How does gauge pressure differ from absolute?
Gauge pressure is usually relative to local atmospheric pressure; absolute pressure is relative to vacuum. With blank or zero p₀ this calculator shows only the increase ρgh relative to the surface; enter actual absolute surface pressure for the total.
Which density should I use?
Fresh water is 1000 kg/m³, sea water about 1025, diesel roughly 840. It is entered because it depends on temperature and composition.
How is this different from the pressure calculator?
That one treats pressure as force divided by area. Here the pressure comes from the weight of a liquid column, and depth enters the formula rather than a contact area.