How to use this calculator
- Enter or choose solve for.
- Enter or choose liquid density.
- Enter or choose density unit.
- Enter or choose depth unit.
- Enter or choose pressure unit.
- The result updates as you type. Use Copy result or Share to keep it.
Method
P_gauge = ρ g h; P_abs = P_surface + ρ g h; h = P_gauge ÷ (ρ g)
- ρ
- liquid density in kg/m³
- g
- gravitational acceleration
- h
- vertical depth below the free surface in m
- P_surface
- pressure acting on the surface (atmospheric if open to air)
Worked example
- P_gauge = 1,000 × 9.80665 × 10 = 98,066.5 Pa = 98.0665 kPa.
- P_abs = 101.325 + 98.0665 = 199.39 kPa, about 1.97 atm.
Ten metres down in fresh water the pressure is about 98 kPa above atmospheric, so roughly double the surface pressure in absolute terms.
What the result means
Divers use the rule of thumb that every 10 m of seawater adds about one atmosphere. Tank walls and dams must resist pressure that grows linearly with depth, so the bottom carries the most load.
Assumptions and limits
- Liquid at rest with constant density (incompressible).
- Density changes with temperature and salinity; very deep ocean water is slightly compressed.
- Not for moving fluids; see the Bernoulli Equation Calculator.
Questions
Does the shape of the container matter?
No. Pressure depends only on the vertical depth, not on the volume or shape above (the hydrostatic paradox).
What is the difference between gauge and absolute pressure?
Gauge pressure is measured relative to the atmosphere; absolute pressure includes it. Tyre gauges read gauge pressure.