How it’s calculated
In a static fluid of constant density, pressure increases linearly with depth because each layer supports the weight of the fluid above it. Gauge pressure is relative to the surface pressure; absolute pressure adds it. Assumes an incompressible liquid at rest and standard gravity g = 9.80665 m/s².
Example (OpenStax University Physics, Section 14.1): the average depth of water behind an 80 m dam is 40 m, so the average gauge pressure is 1000 × 9.8 × 40 = 3.92 × 10⁵ Pa (392 kPa). With g = 9.80665 m/s² this calculator gives 392.3 kPa.
Rule of thumb for fresh water: about 9.81 kPa per meter, or 0.433 psi per foot of depth.
Frequently asked questions
Does the shape of the tank matter?
No. Hydrostatic pressure depends only on depth, density and gravity (the hydrostatic paradox), not on the volume or shape of the container.
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to the atmosphere (what most pressure gauges read). Absolute pressure adds atmospheric pressure, about 101.3 kPa or 14.7 psi at sea level.
How much pressure is 10 m of water?
About 98 kPa (14.2 psi) gauge, roughly one extra atmosphere.
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Sources
- University Physics Vol. 1, 14.1 Fluids, Density, and Pressure — OpenStax
- DOE Fundamentals Handbook: Thermodynamics, Heat Transfer, and Fluid Flow, Vol. 3 — U.S. Department of Energy
Formulas are taken from the free public references above. Results are provided “as is” for informational and educational purposes only. See our disclaimer.
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