RF Skin Depth Calculator

About this calculator

At high frequencies, alternating current in a conductor doesn't flow evenly through the whole cross-section — it crowds toward the surface, a phenomenon called the skin effect. Skin depth (δ) is the distance below the surface where current density has dropped to about 37% (1/e) of its surface value, calculated as δ = √(1/(π·f·μ·σ)), where f is frequency, μ is the material's permeability, and σ is its conductivity.

Higher frequency, higher conductivity, or higher permeability all shrink the skin depth, meaning the current effectively uses only a thin outer shell of the conductor. RF and microwave engineers rely on this figure when designing antennas, PCB traces, and waveguides — since a conductor thicker than a few skin depths wastes material, and PCB trace resistance at RF frequencies must be calculated from the skin depth, not the full trace thickness.