At high frequencies, current crowds near the surface of a conductor – the skin effect. In copper the current is mostly within 8.5 mm of the surface at 60 Hz, but only 2 µm at 1 GHz. That is why RF cables are often silver-plated and Litz wire is made of many thin strands.
How to use the Skin Depth Calculator
- Conductor
- Resistivity ρ
- Relative permeability μ_r
- Frequency f
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Choose the conductor or enter its resistivity and relative permeability, then the frequency.
Inputs explained
| Field | What to enter |
|---|---|
| Conductor | Choose one: Copper, Aluminium, Gold, Silver … |
| Resistivity ρ | Units: Ω·m, µΩ·cm |
| Relative permeability μ_r | A number |
| Frequency f | Units: MHz, kHz, GHz, Hz |
Example values
How the main result changes when Resistivity ρ changes and everything else stays at the example values above:
| Resistivity ρ (Ω·m) | Skin depth δ (µm) |
|---|---|
| 8.4000e-9 | 65.2343 |
| 1.2600e-8 | 65.2343 |
| 1.6800e-8 | 65.2343 |
| 2.1000e-8 | 65.2343 |
| 2.5200e-8 | 65.2343 |
| 3.3600e-8 | 65.2343 |
Formula
δ = √(ρ / (π·f·μ₀·μ_r))
Worked example
Inputs — Conductor: Copper; Frequency f: 1 MHz.
Results — Skin depth δ = 65.23431 µm.
Key terms
- Skin effect
- Concentration of AC current near a conductor's surface.
Frequently asked questions
What is the skin depth of copper at 50 Hz?
About 9.2 mm.
Why does current avoid the centre?
Eddy currents oppose changes of current deep inside.
Why are magnetic metals worse?
High permeability shrinks the skin depth dramatically.
How is the skin effect reduced?
With Litz wire or hollow and plated conductors.