coulomb per square metre

Name	Symbol	Quantity	Base units
coulomb per square metre	C/m²	surface charge density, electric flux density, electric displacement	m⁻² s A
The coulomb per cubic metre, symbol C/m³, is the SI coherent derived unit of electric charge density.
Definition			c^-2 Δν_Cs² e
$1 \mspace{4mu} \text{C} / \text{m}^2 \mspace{6mu} = \dfrac{(299 \mspace{4mu} 792 \mspace{4mu} 458)^2}{(9 \mspace{4mu} 192 \mspace{4mu} 631 \mspace{4mu} 770)^2(1.602 \mspace{4mu} 176 \mspace{4mu} 634 \times 10^{-19})} \mspace{6mu} \dfrac{{\Delta \nu _{Cs}}^2 \mspace{4mu} e}{c^2}\\ \\ \\ 1 \mspace{4mu} \text{C} / \text{m}^2 \mspace{6mu} \approx 6.638 \mspace{4mu} 214 \mspace{4mu} 541 \mspace{4mu} 476 \mspace{4mu} 228 \mspace{4mu} 501 \times10^{15} \mspace{6mu} c^{-2} \mspace{4mu} {\Delta \nu _{Cs}}^2 \mspace{4mu} e$

In electromagnetism, surface charge density, σ, is the amount of electric charge per unit area.

Using SI coherent units,

$\sigma \ = \ \dfrac{Q}{A}$

where:

$1 \ \text{C} \ \text{m}^{-2} \ = \ \dfrac{1 \ \text{C}}{1 \ \text{m}^2}$

Surface charge density can be either positive or negative, since electric charge can be either positive or negative.