Free · Fluid mechanics calculators 💧

Water Column Gauge Pressure and Depth

Find hydrostatic gauge pressure or recover water depth using fresh-water and salt-water density choices, standard gravity and twelve pressure units.

Formula & worked example
Private in your browser
No signup

Go to tool

Calculator inputs

Loading calculator…

How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
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

A 10 m column at the fresh-water preset of 1000 kg/m³ adds 98.0665 kPa of gauge pressure; the salt-water preset of 1025 kg/m³ gives 100.5181625 kPa.

Gauge pressure Δp = ρ g₀ h; depth h = Δp/(ρ g₀), with conventional standard gravity g₀ = 9.80665 m/s².

Worked example

Enter these known values and leave the other values blank.

Water column depth: 10 m

Hydrostatic gauge pressure: 98.07 kPa

Assumptions and limitations

This is the pressure added by a stationary, uniform-density water column below its surface. It uses conventional standard gravity 9.80665 m/s²; actual local gravity can differ.
The retained density selector starts locked at fresh water, 1000 kg/m³, and also offers salt water, 1025 kg/m³. These are fixed modeling approximations, not a salinity or temperature dataset. Actual density depends on temperature, salinity and pressure.
Gauge pressure excludes the pressure acting on the surface. To obtain absolute pressure, add the actual surface pressure separately. The result does not automatically include one atmosphere.
Enter either positive depth or positive gauge pressure and leave the other unknown. The water selector supplies one of two fixed density assumptions; it is not an editable-density or water equation-of-state control.
The retained operating domain requires positive depth, positive gauge pressure and positive density. Surface depth zero and zero gauge pressure are excluded because inverse density at the surface is not uniquely determined.
Pressure units use exact SI prefixes, bar, standard atmosphere and torr; psi uses the international inch and standard pound-force. Technical atmosphere is 98066.5 Pa. Mercury-column units use the conventional 0°C density 13595.1 kg/m³ and standard gravity; torr and mmHg are distinct conventions.
The constant-density approximation does not model deep-ocean compression, layered liquids, moving-water losses or transient loads. Changing a unit does not extend those physical assumptions.

Common questions

Does 10 meters of water give absolute pressure or gauge pressure?

The fresh-water preset gives 98.0665 kPa of gauge pressure. Add the pressure on the surface to find absolute pressure; a surface pressure of 101.325 kPa would give 199.3915 kPa absolute.

Why does salt water give a different pressure?

The salt-water preset has greater assumed mass density: 1025 instead of 1000 kg/m³. The same column therefore weighs more per unit area and adds 2.5% more pressure.

Can pressure be used to find depth?

Yes. Choose the appropriate density preset, enter the positive gauge pressure and leave depth blank. The inverse divides pressure by density times standard gravity.

References

Use conventional standard gravity 9.80665 m/s² throughout the complete hydrostatic forward/inverse graph, preserving the captured fixed water-density presets and depth/pressure relationship. Replace three rounded pressure conversions with exact pound-force/inch, technical-atmosphere and conventional mercury-column definitions; retain positive depth and gauge pressure and explicitly reject nonpositive inferred density.

Explore fluid mechanics calculators 💧 or browse all physics calculators.