Soil Bulk Density & Porosity Calculator

Solves ρ_b = M_s / V_b for bulk density, dry mass, or bulk volume, and uses the result to compute soil porosity — the fraction of a soil's volume available to store water and air. Useful for interpreting core samples, compaction checks, or any soil physics problem needing bulk density.

Bulk Density

ρ_b = M_s / V_b

Solve for

Bulk density Dry mass Bulk volume

Dry soil mass (M_s)

Bulk sample volume (V_b)

Bulk density (ρ_b)

g/cm³

Report answer in

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Porosity

φ = (1 − ρ_b / ρ_p) × 100%

Particle density (ρ_p)

g/cm³

2.65 g/cm³ is a common default for mineral soils — lower for soils with more organic matter.

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Porosity (pore space) — — soil solids

About this calculator

Bulk density (ρ_b) is the mass of dry soil per unit of undisturbed (bulk) volume — it reflects how tightly packed the soil is, including its pore space. Porosity (φ) is the fraction of that bulk volume made up of pores (voids that can hold air or water), calculated from bulk density and particle density:

ρ_b = M_s / V_b — φ = (1 − ρ_b / ρ_p) × 100%

Higher bulk density means less pore space, which generally means less capacity to store water and more resistance to root growth — a common way to flag soil compaction. Pick which quantity you want to solve for (bulk density, dry mass, or bulk volume), enter the other two, and the porosity below updates automatically from whichever bulk density results.

Textbook Example 2.1: An undisturbed soil sample with a volume of 80 cm³ has a dry mass of 100 g. Bulk density = 1.25 g/cm³; porosity = 53% (47% soil particles, 53% pore space). Click "Load textbook Example 2.1" above to see it worked through.