Hydrostatic Pressure Calculator
Calculate the pressure at depth in a fluid from its density, depth and the pressure at the surface.
How it works
P = P₀ + ρ·g·h · gauge pressure = ρ·g·h
Pressure in a fluid increases with depth because each layer must support the weight of everything above it. The extra pressure below the surface, ρ·g·h, is the gauge pressure; adding the surface pressure P₀ gives the total absolute pressure. It depends only on depth and density, not on the shape or width of the container.
Worked example
At 10 m underwater (ρ = 1,000 kg/m³, g = 9.81, surface 101,325 Pa): gauge = 1,000 × 9.81 × 10 = 98,100 Pa, so total ≈ 199,425 Pa — nearly two atmospheres.
Sources: Pressure — Wikipedia
Frequently asked questions
Why does pressure not depend on container shape?
Hydrostatic pressure depends only on depth, gravity and density. A narrow tube and a wide lake have the same pressure at the same depth — the hydrostatic paradox.
What is the difference between gauge and absolute pressure?
Gauge pressure (ρgh) is the pressure above the surface value. Absolute pressure adds the surface pressure P₀ on top, so it is what a sealed gauge referenced to vacuum would read.
How much does pressure rise per metre of water?
About 9,810 Pa per metre, or roughly 0.1 atmosphere. So every 10 m of water depth adds close to one full atmosphere of pressure.
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