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Online Calculator: Pressure @ Depth (not operational)

{CalQlata © 12/04/22}

Enter the ambient density and depth in the preferred units:
The blue values.
You may enter your input data in any of the units provided (this calculator will fill in all the others), but if you do not delete the unwanted inputs between calculations, this calculator will default to the left-most and upper-most values for the next calculation.

Gravitational Acceleration: Tensile Modulus: Poisson's ratio: K:
metric (m/s²) imperial (ft/s²) metric (N/m²) imperial (lb/in²)
Outside Diameter: Wall Thickness:
metric (m) imperial (ins) metric (m) imperial (ins)
ρ Units: Depth: Units: Force Pressure (pc): Units: Mass Pressure: Units: Max Length: Units:
kg/m³ m N/m² kg/m² m:
kg/mm³ mm N/mm² kg/mm² mm
lb/in³ in lbf/in² lb/in² ins
lb/ft³ ft lbf/ft² lb/ft² ft


This Pressure@Depth calculator is accessible from anywhere in the website using the shortcut key; "Alt" + "r".
The "Reset" button clears all calculations on the page and reinstalls default values (this button may not respond in the FireFox browser).
Reset can also be achieved by pressing the "F5" key.
Hover your cursor over the symbols for an associated description.

Pressure at Depth

The pressure within a liquid (or gas) at any given depth is dependent upon its density, at that depth;
This calculator assumes that the liquid is incompressible (i.e. not a gas), which is not strictly true. Some liquids are indeed compressible, but their compressibility is (as in solids) negligible in practical terms.

The difference between Force Pressure and Mass Pressure is that force pressure includes gravitational acceleration and mass pressure does not.

The maximum length is the longest length of pipe between stiffening rings that can be expected to survive at the depth entered. I.e. longer lengths should be supported with stiffening rings at intervals less than this length.


The failure of a thin-wall tube (or pipe) exposed to external pressure is always due to elastic instability, which is always due to out-of-roundness. This is accounted for in such calculations by applying a factor; 'K' to the theoretical collapse pressure (pc; shown above).
But its definition varies throughout the industry as can be seen in the following examples:

pc = ¼ . E/(1-ν²) . (t/r)³ (4)
pc = K.E.(t/dₒ)³ = K.E/8 . (t/rₒ)³ (3)
pc = 5.021E+07 . (t/dₒ)³ {Imperial units} (2)
pc = 8.pc / E.(t/rₒ)³ = (3)
pc = 3.462E+11 . (t/d)³ {metric units} (2)
Giving the following formulas for 'K':
K = 2/(1-ν²) = 5.021E+07 / 3E+07 = pc / E.(t/dₒ)³ = 8.pc / E.(t/rₒ)³

The following comparison results are based upon dimensions; OD = 0.5; t = 0.005; E = 2.07E+11; μ = 0.3 (metric units)
K = 2.197802198 or 1.672368908 or 2.265077257 or 2.333711363

This calculator utilises the following formula:
K = 2/(1-ν²)
as it represents the most conservative of the most comparable results.


You may enter the density in kg/m³ and the depth in inches if you like. This calculator will convert the entered values and print them out accordingly.

Gravitational acceleration, tensile modulus and Poisson's ratio may be altered as you like, but if the calculator is reset (see above), they will revert to the default values.
If after a calculation you wish to alter either the metric of or Imperial values, it would be advisable to delete the unwanted value(s) to ensure that the correct value is used for the next calculation.

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