Grounding & Bonding
Skin depth calculator
At DC, current fills a conductor evenly. At RF, it crowds into a thin layer at the surface — and above a few megahertz that layer is thinner than a human hair. This tool calculates how thin, for the materials you actually meet on the bench.
What skin depth means
Alternating current generates a changing magnetic field inside the conductor, and that field pushes the current back out toward the surface. The faster the alternation, the harder the push. The skin depth δ is the depth at which the current density has fallen to about 37% (1/e) of its surface value:
where ρ is the material's resistivity and µᵣ its relative permeability. Roughly 86% of the current flows within the first two skin depths, so for most purposes the conductor might as well be a hollow tube δ-thick.
Three practical consequences. Bonding: the effective resistance of a strap rises with frequency because less metal carries the current — surface area and surface condition matter more than cross-section. Plating: a few tens of microns of tin or zinc is enough to carry essentially all the RF current, which is why plated finishes and their corrosion state dominate RF bond quality. Shielding: a shield attenuates fields by roughly 8.7 dB per skin depth of thickness, so even thin metal is a very effective shield at high frequency — and note how magnetic materials like steel trade higher resistivity for enormous µᵣ, giving them smaller skin depths than copper.
Inputs
Top: the material's skin-depth law — this curve belongs to the material, so changing frequency moves the amber marker along it rather than reshaping it; change the material to reshape the curve. Bottom: a 2 mm-thick conductor cross-section, with the current-carrying skin drawn to scale at your chosen frequency.
Values assume a solid, clean, non-corroded conductor and a uniform plane-wave view of the field. Surface roughness, plating porosity and corrosion all reduce real-world performance — which is exactly why bond condition gets inspected, not assumed.