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Density Conversion Table



lb/cu in

lb/cu ft




1 lb/cu in






1 lb/cu ft






1 lb/gal

4.33 (10-3)





1 gm/cu cm






1 gm/liter







Courtesy Of: The American Vacuum Society

Density Conversions:


1g/cm3=0.0361 lb/in3(pound per cubic inch)

Courtesy Of: Dr. R. M. German, Powder Metallurgy Science, Second Edition

General Definitions:

  • Density: One of the most common density measurements involves the determination of the geometric space occupied within the envelope of a solid material... including any interior voids, cracks or pores. This is called geometric, envelope or bulk density and only equals true density when there are no internal openings in the material being measured. 

  • Absolute Density:
    1) The ratio of the mass of a volume of solid material to the same volume of water.
    2) The mass per unit volume of a solid material expressed in grams per cubic centimeter.

  • Apparent Density: The weight of a unit volume of powder, usually expressed as grams per cubic centimeter, determined by a specific method

  • Bulk Density: Powder in a container or bin expressed in mass unit per volume

  • Density Ratio: The ratio of the determined density of a compact to the absolute density of metal of the same composition, usually expressed as a percentage. Also referred to as a percent theoretical density

  • Dry Density: The mass per unit volume of an unimpregnated sintered part

  • Green Density: The density of a green compact

  • Packed Density: Please see preferred term of tap density

  • Tap Density: The density of a powder when the volume receptacle is tapped or vibrated under specified conditions while being loaded. Each particle of a solid material has the same true density after grinding, milling or processing, but more geometric space is occupied by the material. In other words, the geometric density is less... approaching 50% less than true density if the particles are spherical. Handling or vibration of powdered material causes the smaller particles to work their way into the spaces between the larger particles. The geometric space occupied by the powder decreases and its density increases. Ultimately no further natural particle packing can be measured without the addition of pressure. Maximum particle packing is achieved. Under controlled conditions of tap rate, tap force (fall) and cylinder diameter, the condition of maximum packing efficiency is highly reproducible. This tap density measurement is formalized in the British Pharmacopoeia method for Apparent Volume, ISO 787/11 and ASTM standard test methods B527, D1464 and D4781 for tap density.

  • True Density: The true density of powders often differs from that of the bulk material because the process of comminution, or grinding will change the crystal structure near the surface of each particle and therefore the density of each particle in a powder. In addition, voids at the surface of a particle, into which liquids will not penetrate, can generate apparent volume which will cause serious errors when density is measured by liquid displacement. The pycnometers from Quantachrome are specifically designed to measure the true volume of solid materials by employing Archimedes' principle of fluid (gas) displacement and the technique of gas expansion. True densities are measured using helium gas since it will penetrate every surface flaw down to about one Angstrom, thereby enabling the measurement of powder volumes with great accuracy. The measurement of density by helium displacement often can reveal the presence of impurities and occluded pores which cannot be determined by any other method.

  • Wet Density: The mass per unit of volume of a sintered part impregnated with oil or other nonmetallic material