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Pressure at Depth Calculator

Find the pressure at depth.

Result

301,658 Pa
301.66 kPa

How it is calculated

The pressure added by a column of liquid is P = ρ × g × h. ρ is the fluid density in kg/m³ (about 1000 for fresh water, a little more for sea water), g is fixed at 9.81 m/s² and h is the depth in metres. The result is the pressure from the liquid alone (gauge pressure), shown in pascals and kilopascals. Atmospheric pressure on the surface is not included, so absolute pressure at depth is higher. If the density is empty, zero or negative, the tool uses 1000 kg/m³. Pressure grows linearly with depth and does not depend on the shape of the container.

Worked example

Sea water with a density of 1,025 kg/m³ at a depth of 30 m. Pressure: 1,025 × 9.81 × 30 = 301,658 Pa (rounded to a whole pascal), which is 301.66 kPa. That is roughly three times normal atmospheric pressure from the water alone, so a diver at this depth also feels the air pressure above the surface added to it.

Try this example →

Common mistakes

  • Treating the result as total (absolute) pressure. The atmosphere above the water is not added.
  • Entering depth in feet or centimetres. The field is in metres.
  • Leaving density as the fresh-water default for sea water, brine or oil, which can be off by several percent or more.
  • Expecting a wider container to produce more pressure. Only depth and density matter, not the volume.

Sources

About this calculator

This calculator finds hydrostatic pressure at a given depth using P = P₀ + ρgh, where P₀ is the pressure at the surface (usually atmospheric), ρ is the fluid's density, g is gravitational acceleration, and h is depth. Pressure increases linearly with depth because of the growing weight of fluid above.

Divers and diving instructors use it to understand pressure changes underwater, engineers use it to design tanks, dams, and submersible equipment, and physics students use it for fluid mechanics coursework.

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Comments (1)

  • Editorial team

    A useful anchor: every 10 m of fresh water adds about 98 kPa, close to one atmosphere, which is 101.3 kPa. So at 30 m in fresh water the water alone gives about 294 kPa, and adding the atmosphere gives roughly 395 kPa absolute. This tool reports only the water's share. If you are designing a tank or a pump intake, say which depth range matters to you.

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