Specific gravity

Specific Gravity (SG) is a special case of relative density.

It is defined as the ratio of the density of a given substance, to the density of water (H2O). Substances with a specific gravity greater than 1 are heavier than water, and those with a specific gravity of less than 1 are lighter than water.

[1]

SG is by definition dimensionless and therefore not dependent on the system of units used (e.g. slugsft−3 or kgm−3), assuming that the units are consistent. Based on the SG-value of a given substance, the density of that substance can be calculated.

  1. The density of the denominator, or reference, is = 1000kgm-3 (at 4°C/39.2°F) in SI units.

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