Surface Charge Density Calculator
Charge spread over a surface. Scientific notation like 2e-6 works.
Where it matters
σ = q / A
On a conductor, charge crowds the surface and σ sets the electric field just outside (E = σ/ε₀). Charge piles up densest on sharp points, which is the whole working principle of lightning rods and the reason high-voltage hardware is built round and smooth.