Void Ratio Calculator

About this calculator

The void ratio (e) of a soil sample is the volume of voids (air and water-filled space between particles) divided by the volume of solids: e = Vv ÷ Vs. It’s closely related to porosity (n), which expresses the same voids as a fraction of total volume instead, via n = e ÷ (1 + e) — the two describe the same physical property from different denominators and are used interchangeably depending on the calculation at hand.

Geotechnical engineers measure void ratio from lab tests on soil samples, often derived from specific gravity, dry unit weight, and moisture content, to assess how compressible or how well-compacted a soil is, since a lower void ratio generally means a denser, stronger soil less prone to settlement under a foundation’s load. It’s a standard input in soil classification, compaction control on construction sites, and settlement calculations for building and pavement foundations.

This calculator takes the void and solid volumes of a soil sample and returns both the void ratio and the corresponding porosity.