What is skin depth (skin effect)?

Skin depth (δ) is the characteristic depth where AC/RF current density decays inside a conductor. Higher frequency or higher permeability results in smaller δ, meaning current concentrates near the surface.

What formula does this skin depth calculator use?

A common approximation is δ = √( ρ / (π · f · μr · μ0) ), where ρ is resistivity (Ω·m), f is frequency (Hz), and μ0 = 4π×10^-7.

How does skin depth relate to PCB copper thickness?

If copper thickness is much larger than δ, current mostly flows near the surface and increasing thickness gives diminishing returns for AC resistance. Width, surface roughness, plating and geometry become more important.

Skin Depth Calculator

Calculate skin depth (δ) from material resistivity, relative permeability, and frequency.

Material

Resistivity ρ

μΩ·cm

Copper at room temperature: ~1.724 μΩ·cm

Relative Permeability μr

Non-magnetic metals are typically ~1

Frequency f

Result

Skin Depth:
- μm

Notes

Formula

Skin depth: δ = √( ρ / (π · f · μr · μ0) )

μ0 = 4π × 10^-7 H/m.

Tips

ρ input unit is μΩ·cm; it is converted to Ω·m automatically
Higher μr will significantly reduce the skin depth
Results are for engineering estimation only

Skin Effect Use Cases

Why calculate skin depth?

At high frequencies, current crowds toward the conductor surface. This increases AC resistance and loss. A skin depth calculator helps estimate how deep the current penetrates for different materials and frequencies, which is useful for PCB traces, copper foil thickness, plating (gold/silver), microstrip/stripline conductors and RF cables.

FAQ

Q: What does a smaller δ mean?
A: More current is confined to the surface, which generally increases conductor loss.

Q: How should I choose material values?
A: Use presets (Copper/Aluminum/Gold/Silver/Nickel) or input custom ρ and μr. Real values may vary with temperature and alloy composition.

Q: Why display results in μm?
A: In the MHz–GHz range, skin depth is typically a few to tens of micrometers for common metals.