Copper aluminum equivalent resistance calculator

Preliminary estimate

Inputs

Calculation note

This compares resistance only. Ampacity, terminal markings, product data, insulation rating, and installation rules are separate checks.

Method

Equivalent area = entered area x target material resistivity / source material resistivity

Aluminum area for equal resistance is about 1.64 x copper area

Copper area for equal resistance is about 0.61 x aluminum area

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Formula variables

  • Entered area is the source conductor cross-sectional area in mm2.
  • Source material is the material being converted from.
  • Target material is the material being converted to.
  • The result matches resistance only, not ampacity or code permission.

Assumptions

  • The calculation compares material resistivity only.
  • Equivalent area does not mean equivalent ampacity, terminal compatibility, insulation rating, or allowable installation.
  • Standard conductor sizes, product markings, temperature, and installation conditions still govern actual conductor selection.
  • Use manufacturer data and applicable project review before substituting conductor material.

Examples

Copper to aluminum. A 16 mm2 copper area needs about 26.23 mm2 aluminum area to match resistance before rounding to a real conductor size.

Aluminum to copper. A 25 mm2 aluminum area corresponds to about 15.25 mm2 copper area by resistance only.