Editing Density (section)

== Units <span class="anchor" id="Unit"></span> ==
From the equation for density ({{math|1=''ρ'' = ''m''/''V''}}), mass density has any unit that is ''mass divided by volume''. As there are many units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The [[SI]] unit of [[kilogram per cubic metre]] (kg/m<sup>3</sup>) and the [[cgs]] unit of [[gram]] per [[cubic centimetre]] (g/cm<sup>3</sup>) are probably the most commonly used units for density. One g/cm<sup>3</sup> is equal to 1000&nbsp;kg/m<sup>3</sup>.  One cubic centimetre (abbreviation cc) is equal to one millilitre. In industry, other larger or smaller units of mass and or volume are often more practical and [[US customary units]] may be used. See below for a list of some of the most common units of density.

The litre and tonne are not part of the SI, but are accepted for use with it, leading to the following units:
* [[kilogram]] per [[litre]] (kg/L)
* [[gram]] per [[millilitre]] (g/mL)
* [[tonne]] per cubic metre (t/m<sup>3</sup>)

Densities using the following metric units all have exactly the same numerical value, one thousandth of the value in (kg/m<sup>3</sup>). Liquid [[water]] has a density of about 1&nbsp;kg/dm<sup>3</sup>, making any of these SI units numerically convenient to use as most [[solid]]s and [[liquid]]s have densities between 0.1 and 20&nbsp;kg/dm<sup>3</sup>.
* kilogram per cubic decimetre (kg/dm<sup>3</sup>)
* gram per cubic centimetre (g/cm<sup>3</sup>)
** 1 g/cm<sup>3</sup> = 1000&nbsp;kg/m<sup>3</sup>
* megagram (metric ton) per cubic metre (Mg/m<sup>3</sup>)

In [[US customary units]] density can be stated in:
* [[Avoirdupois ounce]] per [[cubic inch]] (1&nbsp;g/cm<sup>3</sup> ≈ 0.578036672&nbsp;oz/cu&nbsp;in)
* [[Avoirdupois ounce]] per [[fluid ounce]] (1&nbsp;g/cm<sup>3</sup> ≈ 1.04317556&nbsp;oz/US&nbsp;fl&nbsp;oz = 1.04317556&nbsp;lb/US fl&nbsp;pint)
* [[Pound (mass)|Avoirdupois pound]] per cubic inch (1&nbsp;g/cm<sup>3</sup> ≈ 0.036127292&nbsp;lb/cu&nbsp;in)
* pound per [[cubic foot]] (1&nbsp;g/cm<sup>3</sup> ≈ 62.427961&nbsp;lb/cu&nbsp;ft)
* pound per [[cubic yard]] (1&nbsp;g/cm<sup>3</sup> ≈ 1685.5549&nbsp;lb/cu&nbsp;yd)
* pound per [[US liquid gallon]] (1&nbsp;g/cm<sup>3</sup> ≈ 8.34540445&nbsp;lb/US gal)
* pound per US [[bushel]] (1&nbsp;g/cm<sup>3</sup> ≈ 77.6888513&nbsp;lb/bu)
* [[slug (unit)|slug]] per cubic foot

[[Imperial units]] differing from the above (as the Imperial gallon and bushel differ from the US units) in practice are rarely used, though found in older documents. The Imperial gallon was based on the concept that an [[Imperial fluid ounce]] of water would have a mass of one Avoirdupois ounce, and indeed 1&nbsp;g/cm<sup>3</sup> ≈ 1.00224129 ounces per Imperial fluid ounce = 10.0224129 pounds per Imperial gallon. The density of [[precious metal]]s could conceivably be based on [[Troy weight|Troy]] ounces and pounds, a possible cause of confusion.

Knowing the volume of the [[unit cell]] of a crystalline material and its formula weight (in [[Dalton (unit)|daltons]]), the density can be calculated. One dalton per cubic [[ångström]] is equal to a density of {{val|1.66053906660|u=g/cm3}}.