Area Density (ρ𝐴) ○◂ Entries

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Area Density (ρ𝐴) ○◂｜Definition｜1st｜20260104120328-00-⌔

Area density - Wikipedia

Area density

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The area density (also known as areal density, surface density, superficial density, column density, or density thickness) of a two-dimensional object is defined as the quotient of mass by area. The SI derived unit is the “kilogram per square metre” (unit symbol kg·m${}^{-2}$).

In the paper and fabric industries, it is called grammage and is expressed in grams per square meter (g/m${}^2$); for paper in particular, it may be expressed as pounds per ream of standard sizes (“basis ream”).

A generalized areic quantity is defined as the quotient of a generic physical quantity by area,¹ such as surface charge density or areic electric charge.² A related area number density can be defined by replacing mass by number of particles or other countable quantity.

Printed 2026-06-28.

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Footnotes

1. “ISO 80000-1: Quantities and units — Part 1: General”. iso.org. Retrieved 2023-10-16. ↩

2. “IEC 80000-6:2022 Quantities and units — Part 6: Electromagnetism”. International Organization for Standardization. Retrieved 2022-11-20. ↩

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