Pressure at Depth Calculator
Pressure underwater (or under any fluid) increases steadily with depth, regardless of the container's shape or size — this is why ear pressure builds the same way whether you're diving in a pool or the ocean, at the same depth.
Inputs
Result
196.2 kPa
Absolute 297.53 kPa · 1.936 atm gauge
How the pressure at depth calculator works
Gauge pressure (pressure due to the fluid alone) = fluid density × 9.81 × depth.
Absolute pressure = gauge pressure + atmospheric pressure (101,325 Pa at sea level).
Worked example: 20 m deep in fresh water (density 1,000 kg/m³)
- Gauge pressure = 1,000 × 9.81 × 20 = 196,200 Pa = 196.2 kPa.
- Absolute pressure = (196,200 + 101,325) ÷ 1,000 = 297.525 kPa.
- In atmospheres (gauge): 196,200 ÷ 101,325 ≈ 1.94 atm — meaning pressure at 20 m is already nearly double what it is at the surface, from the water alone.
Common mistakes to avoid
Confusing gauge pressure with absolute pressure
Gauge pressure is the extra pressure from the fluid alone (what a typical pressure gauge reads, zeroed at the surface); absolute pressure additionally includes atmospheric pressure pressing down from above. Diving and engineering contexts often need to be explicit about which one is meant.
Using seawater density where fresh water was intended, or vice versa
Seawater is denser (roughly 1,025 kg/m³) than fresh water (1,000 kg/m³) — using the wrong value for the actual fluid slightly understates or overstates real pressure, which matters for precise diving or engineering calculations.
Frequently asked questions
Why does pressure increase with depth regardless of container shape?
Pressure at a given depth depends only on the weight of fluid directly above that point, which is determined by depth and density alone — not on the total volume of fluid in a wider or narrower container.
How does this relate to scuba diving safety?
Every 10 m of depth in seawater adds roughly 1 atmosphere of pressure — this rapid pressure increase is why divers must ascend slowly and manage air expansion carefully to avoid decompression sickness.
What's a typical value for atmospheric pressure at sea level?
101,325 Pa (101.325 kPa), also known as 1 standard atmosphere — this is the baseline value this calculator adds to gauge pressure to get absolute pressure.
Does this formula apply to gases as well as liquids?
The same principle applies, but gas density changes significantly with pressure and altitude in a way liquid density mostly doesn't over normal ranges, so atmospheric pressure calculations for gases need a more complex model than this simple linear relationship.
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