Skin Depth Calculator

About this calculator

The skin depth describes how deeply an alternating current penetrates into a conductor before its density falls to 1/e (about 37%) of its surface value, given by δ = √(2ρ / (ωμ)), where ρ is the resistivity, ω = 2πf is the angular frequency, and μ is the permeability of the material. Because δ shrinks as frequency rises, high-frequency AC current tends to flow mostly near the conductor's surface — the "skin effect" — leaving the core of the wire largely unused.

RF and power electronics engineers use skin depth to size conductors for radio-frequency circuits, transformers, and induction heaters, to explain why high-voltage transmission lines and RF cables sometimes use hollow or stranded (Litz) wire instead of solid conductors, and to estimate the effective AC resistance of a wire, which rises with frequency as usable cross-section shrinks. Enter the resistivity, permeability, and frequency to find the skin depth.