Specific Gravity Definition

In physics, specific gravity relates to the substance's densities and water at a precise temperature. It is also called relative gravity. In simple words, specific gravity can also be defined as the ratio between the substance and water densities. Because the specific gravity has no unit, it is dimensionless. Densities are canceled out in a formula when they're expressed as weight per volume, and density units cancel out.


Formula of Specific Gravity

If you want to calculate specific gravity, you can use the formula listed below or jump to our calculator to find your answer instantly.

SG = ρ substance / ρ H2O


SG = Specific Gravity

ρ substance = density of a substance

ρ H2O = density of water


To know how to find out the specific gravity, you can use our Specific Gravity Calculator.


For a more precise understanding of how to find the specific gravity, let us have an example below:

Suppose the density of gasoline is 810 kg/m3. Then find out the specific gravity of the gas.

Given data

The density of gasoline = 810 kg/m3
The density of water = 1000 kg/m3

To Find

The specific gravity of gas = ?


To find the specific gravity of gas, you can use the formula listed below:

SG = ρ substance / ρ H2O

Putting values in the formula:

SG = 810 / 1000 = 0.81