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Equation / Last modified by AndrewS on 2016/11/09 15:36
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This vCalc permeability conversion equation converts the input measure of permeability into your choice of other units of permeability.


Permeability is a measure of the ability of fluids or gases to flow through rock (or other porous media). The standard unit of permeability is the darcy and is defined using Darcy's law.

The units of permeability supported by vCalc for conversion are:

  • d (darcy)
  • md ( milli-darcy)
  • `mu`d (micro-darcy)

To perform conversion, enter the numeric number of units you want to convert and pull-down the menu to select the units associated with your input value.

The results will be displayed in the default permeability units and you can pull-down the units selection menu to change the output units to your desired converted units.

For example: if you enter 205.8 and leave the default input units as as your input permeability unit, the display will show a resultant 205.8 d output.  If you then select `mu`d as your output units, the output is automatically converted to 2.058E8 `mu`d .

Example: if you enter 1000 and select `mu`d as input units, you can convert to md  by simply selecting md as the output unit. vCalc would convert 1000 `mu`d to 1.0 md.


The unit of the darcy (d) measures the ability to flow through a medium and is defined by Darcy's Law, which is stated:

     `Q = (A*kappa*DeltaP) / (mu *Deltax)`


  • Q  - the volumetric flow rate through a medium                
  • `Delta`P - the applied pressure difference
  • `Delta`x - the thickness of the medium
  • A - the cross-sectional area of the medium
  • `kappa` - the permeability of the medium
  • `mu` - the dynamic viscosity of the fluid

The darcy is referenced to multiple unit systems. A medium with a permeability of 1 darcy permits a flow of 1 cm³/s of a fluid with viscosity 1 cP (1 mPa·s) under a pressure gradient of 1 atm/cm acting across an area of 1 cm².1

See also: