🪨 Porosity and Permeability Calculator
Enter the bulk volume, void (pore) volume, and average grain diameter of a porous sample to estimate its porosity and permeability.
What This Calculator Does
This tool calculates the porosity of a porous material (like soil, sand, or rock) from its bulk and void volumes, and gives a rough permeability estimate based on porosity and average grain size using the Kozeny-Carman equation.
The Formula
Porosity is the simple ratio φ = Vvoid ÷ Vbulk, expressed as a percentage. Permeability is estimated using the Kozeny-Carman relation, k = (d² × φ³) ÷ (180 × (1−φ)²), where d is the average grain diameter. This gives permeability in square meters, commonly converted to darcys (1 darcy ≈ 9.869 × 10⁻¹³ m²) for practical use.
- The Kozeny-Carman equation assumes a packed bed of roughly uniform, spherical grains and is an approximation, not an exact measurement.
- Actual permeability from lab testing (e.g. a permeameter) can differ significantly due to grain shape, sorting, and cementation.
This uses standard porosity and Kozeny-Carman relationships for general geotechnical and educational reference; use direct lab measurement for engineering-critical work.