**Some commonly used density measuring devices include hydrometers, aerometers, pycnometers, density kits and digital density meters.** The density of an object can be manually computed by dividing its mass by its volume, which is mathematically represented by the formula d = m/v, where "d" denotes density, "m" indicates the mass and "v" is the volume of the object.

Matter is typically defined based on its characteristic rest mass and the space it occupies, also referred to as the "volume." Another physical attribute that distinctly identifies any type of material, be it solid, liquid or gas, is its density. The density of an object pertains to how compact or spread out the particles comprising an object are. Rocks and metals have densities of around 3 g/cm^{3} and 7 g/cm^{3}, respectively. Gases are the least dense among the three phases of matter.

Density can be measured using a variety of instruments. A hydrometer is used to determine the density of a liquid relative to the density of water, which is given as 1 g/cm^{3}. Hydrometers are partially immersed in the sample liquid to measure its density. Some types of hydrometers include Baume hydrometers, API hydrometers, alcohol proof hydrometers and draft survey hydrometers. An aerometer measures the density of air, as well as other gases. A pycnometer also measures a liquid's density using a glass beaker of known volume. A density kit comes with a balance, while a digital density meter determines the density based on frequencies.