Hydrostatic Pressure Calculator
Enter a fluid density and a depth to get the hydrostatic pressure in pascals — plus kilopascals — and see why pressure climbs steadily the deeper you go.
Use SI units
Density in kilograms per cubic metre and depth in metres give pressure in pascals — fresh water is about 1000 kg/m³, seawater about 1025 kg/m³.
What is hydrostatic pressure?
The pressure of a fluid at rest
This hydrostatic pressure calculator turns two measurements — the fluid density in kilograms per cubic metre and the depth in metres — into the pressure a still fluid exerts at that depth, in pascals and kilopascals. Hydrostatic pressure is the pressure a fluid at rest pushes out with because of the weight of the fluid stacked above a point. It acts equally in every direction and depends only on density, gravity, and depth — never on the shape or width of the container. It is the number behind why your ears pop as you dive, why dam walls are built thicker at the base, and how a water tower delivers steady pressure to a whole street.
Enter a fluid density in kg/m³ and a depth in metres to get the hydrostatic pressure in pascals and kilopascals instantly.
Hydrostatic pressure is the fluid density multiplied by the acceleration of gravity and by the depth. We use the standard gravity of 9.80665 m/s².
P = ρ × g × hSuppose you are 10 m below the surface of fresh water (density 1000 kg/m³). Multiply the density by gravity, 1000 × 9.80665 = 9806.65, then by the depth, 9806.65 × 10 = 98,066.5 Pa. Dividing by 1000 gives 98.0665 kPa — close to one standard atmosphere, which is why ten metres of water roughly doubles the absolute pressure on a diver. Because the formula is linear in depth, doubling the depth to 20 m simply doubles the pressure to 196,133 Pa.
The formula is exact for a fluid at rest, but a few practical points are worth keeping in mind.
Gauge pressure, constant density, and fluid at rest
P = ρgh gives the gauge pressure from the fluid alone — add the atmospheric pressure at the surface (about 101,325 Pa at sea level) for the absolute pressure. It assumes the density stays constant with depth, which is fine for liquids but not for gases, and that the fluid is still: moving or accelerating fluids need the fuller Bernoulli or Navier–Stokes treatment. Keep your units consistent — kilograms per cubic metre for density and metres for depth — or the pascals will be wrong.