Hydrostatic Pressure Calculator

Hydrostatic pressure is the pressure created by the weight of a fluid at rest. Every layer of liquid supports the layers above it, so pressure increases as a measurement point moves deeper below the free surface. The basic relationship is p = rho × g × h, where rho is fluid density in kilograms per cubic metre, g is gravitational acceleration in metres per second squared, and h is vertical depth in metres. Multiplying those SI quantities produces pressure in pascals. This hydrostatic pressure calculator evaluates gauge pressure, meaning pressure caused only by the liquid column. It does not automatically add atmospheric pressure at the surface. To obtain absolute pressure in an open tank, add the local atmospheric pressure to the displayed gauge pressure. Standard sea-level atmospheric pressure is approximately 101,325 pascals, but weather and elevation change that value. Closed vessels may have a different surface pressure, which should likewise be added separately. Density is the key material property. Fresh water near room temperature is often approximated as 1,000 kg/m³, seawater is commonly near 1,025 kg/m³, and many oils fall between roughly 800 and 900 kg/m³. Real density varies with temperature, salinity, composition, and pressure. Use a measured or specified value when the result supports engineering decisions. The default gravitational acceleration, 9.80665 m/s², is standard Earth gravity; it can be changed for local precision or calculations on another celestial body. Depth means vertical distance below the fluid surface, not the sloping distance along a wall or pipe. Container shape and total liquid volume do not affect pressure at a given depth when the fluid is stationary and density is uniform. This sometimes surprising result is called the hydrostatic paradox. However, pressure force on a surface also depends on its area and pressure distribution, so structural analysis requires more than the single pressure value calculated here. The simple formula assumes an incompressible fluid with constant density and a uniform gravitational field. It works very well for ordinary liquid tanks, pools, diving estimates, piezometers, dams, and short liquid columns. Gas columns, very deep liquids, accelerating containers, and fluids with strongly changing density need more detailed models. The calculator reports both pascals and kilopascals, making it easy to compare results with pressure gauges, equipment ratings, and fluid-mechanics examples.