James Yates

Grounding & Bonding

Skin depth calculator

Calculate skin depth from frequency, resistivity and relative permeability for common conductor and plating materials.

What skin depth means

At higher frequencies, alternating current is concentrated nearer the conductor surface. Skin depth δ is the depth at which current density falls to approximately 37% (1/e) of its surface value:

δ  =  ρπ · f · µ₀ · µᵣ

where ρ is resistivity and µᵣ is relative permeability.

Skin effect increases effective AC resistance by reducing the conducting cross-section. Plating thickness and surface condition affect RF current distribution and bond performance. Shield absorption is approximately 8.7 dB per skin depth of thickness in this model; resistivity and permeability determine the skin depth.

Inputs

For steel and nickel this varies a lot with grade, field strength and frequency — treat the presets as ballpark.
Skin depth δ
Depth carrying ~86% of current (2δ)
Shield attenuation per mm (absorption)

The upper plot shows skin depth against frequency for the selected material. The marker indicates the selected frequency. The lower plot shows skin depth to scale in a 2 mm-thick conductor.

Values assume a solid, clean conductor and uniform plane-wave conditions. Surface roughness, plating porosity and corrosion can affect performance.