🌊 Pressure ⇄ Depth Converter
Convert pressure readings into equivalent depth of liquid, or convert depth back into hydrostatic pressure.
Converter Tool
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Understanding Pressure and Depth
Hydrostatic pressure is the pressure exerted by a fluid column due to its weight. When you go underwater, each meter of depth adds extra pressure from the water above.
The Formula
P = ρ g h
- P = pressure (Pa)
- ρ = density of fluid (kg/m³)
- g = gravitational acceleration (9.81 m/s²)
- h = depth (m)
Rearranging: h = P / (ρ g)
Effect of Fluid Density
The deeper you go, the more the pressure rises. But different fluids have different densities:
| Fluid | Density (kg/m³) | Depth per 1 atm |
|---|---|---|
| Freshwater | 1000 | 10.3 m |
| Seawater | 1025 | 10.1 m |
| Mercury | 13,600 | 0.75 m |
| Oil | 850 | 12.1 m |
Applications
- Diving: Depth gauges use this principle.
- Engineering: Dam and submarine design depends on hydrostatic forces.
- Medicine: Pressure is related to fluid levels in manometers.
- Hydraulics: Pressure sensors can be calibrated against fluid columns.
Limitations
This calculator assumes constant density and ignores compressibility of fluids. At great depths (km scale), compressibility and salinity changes matter.
FAQ
How many meters per bar in seawater?
About 10.1 m.
How many psi per foot?
Each foot of water adds ≈ 0.433 psi.
Does this include atmospheric pressure?
No, results are relative (gauge pressure). Add 1 atm for absolute values.
Why is seawater different from freshwater?
Because of dissolved salts, seawater is denser, so pressure rises faster with depth.
What if fluid is oil?
Oil has lower density, so depth increases more slowly per unit pressure.
Case Studies
Scuba diving: A diver at 30 m in seawater experiences ~4 atm pressure (1 atm air + 3 atm water). Dams: Engineers calculate pressure at the base to design concrete thickness. Medical: Blood pressure manometers are calibrated in cmHg using the same principle.
Conclusion
The relation between pressure and depth is one of the most direct and practical applications of physics. Whether in ocean exploration, engineering, or medicine, the ability to convert between pressure and depth is essential.