Soil Void Ratio Calculator

Void ratio versus porosity

Void ratio and porosity both describe pore space in soil, but they use different reference volumes - void ratio compares void volume to solid volume, while porosity compares void volume to total volume. Geotechnical engineers favor void ratio because it changes in a simple, linear way as soil compresses under load.

Worked example

For a soil sample with 40 cm³ of void space and 60 cm³ of solid material:

e = 40 / 60 = 0.667

Equivalent Porosity = 0.667 / 1.667 x 100 = 40.0%

Frequently asked questions

Why does geotechnical engineering prefer void ratio over porosity? As soil consolidates under load, its solid volume stays essentially constant while void volume shrinks - this makes void ratio change in direct proportion to compression, simplifying the math in consolidation and settlement calculations compared to porosity.

Can void ratio exceed 1.0? Yes - very loose, uncompacted soils (like some fresh clay deposits) can have void ratios well above 1.0, meaning more than half their volume is pore space rather than solid material.