Hydrostatic pressure increase
Relative to surface pressure; no atmospheric pressure is added.
Fluid mechanics · Hydrostatics
Hydrostatic pressure calculator
Calculate the pressure increase below a fluid surface, or infer depth from that pressure increase. Δp = ρgh is relative to the surface pressure; it is not absolute pressure.
Created v1.0
By Thibaut Grzelak, Mechanical Analysis Engineer
02
Results
Depth
Vertical distance below the surface.
Relation and numerical substitution
Δp = ρ × g × h—
Fluid at rest with uniform density and gravity. Depth is measured vertically downward from the surface.
01Formulas and symbols
Formulas used
Δp
Δp = ρ × g × hRelative to surface pressure; no atmospheric pressure is added.h
h = Δp / (ρ × g)Vertical distance below the surface.02Assumptions and limits
Scope of validity
- Fluid at rest with uniform density and gravity. Depth is measured vertically downward from the surface.
03Validation example
Reference numerical case
- 1000 kg/m³ × 9.80665 m/s² × 10 m = 98066.5 Pa, approximately 98 kPa above the surface pressure.
04References
Technical references
FAQ
Is pressure zero at the surface?
The increase Δp is zero at h = 0; absolute surface pressure need not be zero.
Does vessel shape change ρgh?
Not in this model. Pressure at a given depth depends on density and gravity, not the vessel width.
05Model and conventions
Calculate the pressure increase below a fluid surface, or infer depth from that pressure increase. Δp = ρgh is relative to the surface pressure; it is not absolute pressure.
06Limits of this model
No density stratification, compressibility or moving-fluid effects. To obtain absolute pressure, add a known absolute surface pressure separately; 1 atm is never assumed.
07Common mistakes
Use fluid density, not object density, and vertical depth rather than sloping pipe length.