# Specific weights

## Building materials table. Density is the mass per unit volume (kg/m³), while specific gravity is the weight per unit volume (kN/m³) and depends on the acceleration of gravity.

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29 June 2023

### Density and specific weight of some materials

Density is the mass per unit volume (kg/m³), while specific gravity is the weight per unit volume (kN/m³) and depends on the acceleration of gravity. The density and specific gravity of a material can vary with temperature and pressure, so these figures are approximate and may be subject to slight variations in actual conditions.

The following table shows the value of the density (more properly “density”) in kg/m³ and the specific weight in N/m³ of some materials. To obtain the value of the specific weight in N/m³, simply multiply the value of the density by the gravitational acceleration constant, which in the case of the Earth’s gravitational field is approximately 9.81 m/s² (depending on the point on the Earth’s surface where is found, the conventional value has been set at 9.80665 m/s²).

In the following table, where not otherwise indicated, the term “water” means pure water (i.e. without substances dissolved in it, i.e. made up only of H2O molecules). In fact, the specific weight of water varies depending on the substances possibly dissolved in it.
The density values can also be read indifferently as grams per dm³.

Specific gravity is defined as the weight of a sample of material divided by its volume.

In the International System the unit of measurement is N/m³.
The term specific weight is commonly used improperly as a synonym for density and for this reason it is often indicated as g/cm³ or kg/L or kg/dm³.