Soil Bulk Density & Porosity Calculator
Enter the oven-dry mass and total volume of a soil sample to get bulk density, porosity, and void ratio. Optionally add wet mass for gravimetric and volumetric water content.
g
cm³
g/cm³
g
Dry mass per unit total volume — typical range 1.0–1.8 g/cm³ for mineral soils
- 1
Solid volume Vs
150 ÷ 2.65 = 56.604 - 2
Pore volume Vv
100 − 56.604 = 43.396 - 3
Bulk density ρb
150 ÷ 100 = 1.500
此計算機如何運作？
Bulk density ρb = m_dry/V_total; porosity n = 1 − ρb/ρs; void ratio e = n/(1−n). Particle density ρs ≈ 2.65 g/cm³ for mineral soils. Add wet mass for water content θg = (m_wet−m_dry)/m_dry. Typical ρb range: 1.0–1.8 g/cm³.
公式
How this is calculated
Soil consists of solid particles, water, and air. The bulk density (ρb = m_dry / V_total) measures how much dry solid mass is packed into a unit volume of undisturbed soil, including pores. It ranges from about 1.0 g/cm³ (loose, organic-rich soils) to 1.8 g/cm³ (compacted mineral soils). Sandy soils are typically denser; clay-rich or organic soils are lighter.
Porosity n = 1 − ρb/ρs is the fraction of total volume occupied by pores (water + air). Particle density ρs is the density of the solid grains themselves — approximately 2.65 g/cm³ for quartz-rich mineral soils, lower (~2.0–2.4) for soils with significant organic matter. The void ratio e = n/(1−n) is the ratio of pore volume to solid volume, preferred in geotechnical engineering.
If you provide the wet mass (field-moist sample), the calculator also returns gravimetric water content θg = (m_wet − m_dry)/m_dry × 100% (mass of water per mass of dry soil), volumetric water content θv = θg × ρb/ρw (volume of water per total volume, with ρw = 1 g/cm³ for water), and degree of saturation = θv / n × 100%.
常見問題
Optimal bulk density for crop growth is roughly 1.0–1.3 g/cm³ for loamy and clay soils and 1.2–1.6 g/cm³ for sandy soils. Above 1.6–1.8 g/cm³, root penetration is restricted and compaction is considered problematic.
The standard methods are the core method (a cylinder of known volume driven into the soil), the clod method (coating an undisturbed clod in paraffin and measuring water displacement), or the excavation method (measuring the volume of the hole with sand or water). The core method with a known-volume ring is most common in the lab.
Particle density ρs tells you the density of the actual mineral grains — without it, you cannot calculate porosity (the fraction of the volume that is empty pore space). Bulk density alone just tells you how much mass there is per unit volume, which mixes the solid and pore contributions together.
也稱為
TG we-Calculate Editorial Team. (2026). Soil Bulk Density & Porosity Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/zh-tw/calculator/soil-calculator
TG we-Calculate Editorial Team. "Soil Bulk Density & Porosity Calculator." TG we-Calculate. 2026. https://we-calculate.com/zh-tw/calculator/soil-calculator.
TG we-Calculate Editorial Team, "Soil Bulk Density & Porosity Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/zh-tw/calculator/soil-calculator
@misc{wecalculate_soil_calculator, title = {Soil Bulk Density & Porosity Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/zh-tw/calculator/soil-calculator}}, year = {2026}, note = {TG we-Calculate} }
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