Void Ratio [Porosity]

The Void Ratio calculator computes the void ratio of a sample volume.  

INSTRUCTIONS: Enter the following:

• (n) Porosity Percentage

Void Ratio (VR): The calculator returns the ratio as a real number.

The Math / Science

The void ratio represents the relative amount of space occupied by the "voids" in a volume of material, where the voids can be a combination of liquids or gases, and the relative amount of space occupied by the solid component of the sample.  The formula for Void Ratio is:

VR = n / (1-n)

where:

• VR = Void Ratio
• n = porosity percentage

This void ratio is a measure of how compact the material is.  A volume of large rocks will obviously have a great deal of space between them and thus have a large void ratio compared to fine particulate of a volume of a clay soil, which would have very limited amounts of voids relative to the solid matter.

The input to this equation are the porosity percentage, `n` of the sample.

In engineering application the void ratio is used to indicate a tendency of a material to expand or contract.  A high void ratio is likely to be seen in loose soils which then will contract under pressure or added loads.  A low void ratio represents a material that is dense.  This void ratio reflects the affect of how fluids will flow through a medium or how particulates can move through the medium.