Free · Fluid mechanics calculators 💧

Fluid Depth & Hydrostatic Absolute Pressure

Calculate absolute pressure at depth from fluid density, gravity and surface pressure, with reverse solutions and density presets.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

At 10 m in a 1,000 kg/m³ fluid with g = 9.80665 m/s² and surface pressure of 101,325 Pa, absolute pressure is 199,391.5 Pa.

p = p_surface + ρgh

Worked example

Enter these known values and leave the other values blank.

Depth below the surface
10 m
Gravitational acceleration
9.80665 m/s²
Absolute pressure at the surface
1 atm
Density of fluid
1000 kg/m³
Absolute pressure at depth
1.968 atm

Assumptions and limitations

  • The fluid is stationary with uniform density and gravity. This model omits compressibility, flow effects and depth-dependent density.
  • Depth and absolute surface pressure may be zero. Density and gravitational acceleration must be positive.
  • Density presets are illustrative values; temperature and salinity can change them. Use a measured density through Custom when precision matters.
  • At zero depth, pressure equals surface pressure; those two values alone cannot determine density or gravity.

Common questions

Is the output gauge pressure?

The output is absolute pressure. Subtract the entered surface pressure to obtain the hydrostatic pressure increase ρgh.

References

Bookify accepts zero depth and validates positive gravity and nonnegative absolute pressure. Mercury pressure columns use conventional density and standard gravity, with the exact international inch. Pounds-force per square inch use the exact international pound and inch with standard gravity, replacing the rounded captured factor. One technical atmosphere is exactly one kilogram-force per square centimeter under standard gravity. Bookify uses exact customary mass and volume definitions for density units, replacing rounded factors in the reference.

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