Pressure at Depth Calculator (Fluid)
Find the gauge and absolute pressure at a depth in any fluid from its density, the depth and gravity.
How it works
P_gauge = ρ·g·h · P_absolute = P_atm + ρ·g·h
The pressure a fluid exerts rises linearly with depth: every metre of water adds about 9.81 kPa because you are supporting the weight of the column above you. Gauge pressure (ρgh) measures the excess over the surface, while absolute pressure adds the atmospheric pressure pressing on the surface. Density is what makes seawater press slightly harder than fresh water and mercury press far harder than either.
Worked example
At 10 m depth in fresh water (ρ = 1000 kg/m³, g = 9.81 m/s²): gauge = 1000 × 9.81 × 10 = 98,100 Pa ≈ 98.1 kPa. Adding sea-level atmosphere (101,325 Pa) gives an absolute pressure of about 199,425 Pa — very nearly 2 atmospheres.
Sources: Pressure — Wikipedia
Frequently asked questions
Why doesn’t the shape of the container matter?
Fluid pressure depends only on vertical depth, density and gravity — not on the width or shape of the vessel. 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 is measured relative to the surrounding atmosphere, so it reads zero at the surface. Absolute pressure adds atmospheric pressure and is what you use in the gas laws.
Roughly how deep is one extra atmosphere of water?
About 10.3 m of fresh water adds one atmosphere (≈101 kPa). Divers use the rule that pressure increases by roughly 1 bar every 10 m.
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This calculator is for educational purposes. Double-check important results before acting on them.