Last updated October 12, 2026 · Report an error
At higher AC frequencies, current in a conductor increasingly crowds toward the surface rather than flowing evenly through the whole cross-section — a phenomenon called the skin effect. This calculator finds the skin depth (how far current effectively penetrates) for copper or aluminum at a given frequency.
How it works
Choose copper or aluminum and enter the AC frequency, and the calculator applies δ = √(ρ/(πfμ)), using each material's standard resistivity and (since both are non-magnetic) the permeability of free space.
- Enter conductor material.
- Enter frequency (Hz).
- Click Calculate to see your results.
Examples
Mains frequency in copper
At 60 Hz (US mains frequency), copper has a skin depth of about 8.4 mm — for typical household wire gauges, the skin effect is usually negligible at this frequency, but it becomes significant at radio frequencies.
Who should use it
- RF and high-frequency electronics design.
- Electrical engineering coursework on AC conductor behavior.
Industry applications
- RF and high-frequency circuit design
- Power systems and cable engineering
Advantages
- Quick way to check whether skin effect matters for your specific frequency and material.
- Uses standard, correct resistivity values for common conductor materials.
Limitations
- Only covers copper and aluminum — other conductor materials would need their own resistivity value.
Common mistakes to avoid
- Ignoring skin effect in high-frequency (RF, switching power supply) designs where it genuinely increases effective resistance.
- Worrying about skin effect unnecessarily at standard mains frequencies for typical wire gauges, where it's usually negligible.
Best practices
- Compare the calculated skin depth against your actual conductor's radius — skin effect only meaningfully matters once skin depth approaches or falls below that radius.
- For high-frequency designs where skin effect is significant, consider stranded/litz wire, which is specifically designed to reduce skin-effect losses.
Tips
- If your skin depth comes out much smaller than your wire's radius, most of the conductor's cross-section isn't actually carrying current — litz wire or a larger surface-area conductor shape becomes worth considering.