The SI unit for bulk density is kg/m³ (kilograms per cubic meter).
This is consistent across various sources. The bulk density, representing the mass of a substance per unit volume, naturally uses the base SI units for mass (kilogram) and volume (cubic meter). While other units like g/cm³, lb/ft³ (pcf), are commonly used, they are not the standard SI unit.
Several references support this:
- Study.com: Explicitly states that the SI unit for bulk density is kg/m³.[1]
- Agronomy Journal: Points out that densities (including bulk density) have dimensions of M L⁻³, leading to the base SI unit of kg m⁻³ (kg/m³).[2]
- Various other sources: Multiple websites and documents confirm kg/m³ as the SI unit for density, which directly applies to bulk density.[3, 4, 5, 6, 7, 8, 9, 10]
Understanding Bulk Density:
Bulk density is different from particle density. Particle density measures the mass of a material's solid particles only, excluding the space between them (pores). Bulk density, however, accounts for the total volume, including the spaces between particles. This makes bulk density lower than particle density for most materials.
Examples of Bulk Density in Different Units:
- SI Unit: A soil sample with a bulk density of 1500 kg/m³ means that 1 cubic meter of the soil weighs 1500 kilograms.
- Other Units: The same soil sample could also be expressed as 1.5 g/cm³ or approximately 93.6 pcf.
References:
[1] Study.com: https://study.com/learn/lesson/bulk-density-equation-compaction.html
[2] Agronomy Journal: https://www.agronomy.org/files/publications/nse/pdfs/jnr010/010-01-0073.pdf
[3] Wikipedia (Density): https://en.wikipedia.org/wiki/Density
[4] South Dakota State University Extension: https://extension.sdstate.edu/bulk-density-indicator-soil-health
[5] Omnexus: https://omnexus.specialchem.com/polymer-property/density
[6] Quora: https://www.quora.com/What-is-the-SI-unit-of-density-mass-and-volume
[7] Itasca Consulting Group: https://docs.itascacg.com/flac3d700/flac3d/docproject/source/theory/fluid-mechanical/properties_units/properties_units.html
[8] National Physical Laboratory: https://www.npl.co.uk/resources/q-a/density-specific-gravity-differences
[9] Penn State Extension: https://extension.psu.edu/conversion-factors-for-english-and-si-metric-units
[10] Calculator.net: https://www.calculator.net/density-calculator.html
