Area density

The area density (also known as areal density, surface density, superficial density, areic density, column density, or density thickness) of a two-dimensional object is calculated as the <a href="/facts/Mass/HHdc8XmF">mass</a> per unit <a href="/facts/Area/KsNG1G9t">area</a>. The <a href="/facts/SI_derived_unit/RLu52lWy">SI derived unit</a> is the "<a href="/facts/Kilogram/lU2zbPk8">kilogram</a> per <a href="/facts/Square_metre/u5nT9y0W">square metre</a>" (kg·m−2). 
In the paper and fabric industries, it is called <a href="/facts/Grammage/h6vfTXn7">grammage</a> and is expressed in grams per square meter (g/m2); for paper in particular, it may be expressed as pounds per <a href="/facts/Paper_ream/qVMrcm8P">ream</a> of standard sizes ("basis ream").
A related <a href="/facts/Area_number_density/qtyDnLhz">area number density</a> can be defined by replacing mass by <a href="/facts/Number_of_particles/jqVeDoIl">number of particles</a> or other <a href="/facts/Countable_quantity/TINrpQIq">countable quantity</a>, with resulting units of m−2.

Area density open-in-new

Area density