Convert Ohm Circular Mils per Foot to Ω·mm²/m

Formula

Ω·mm²/m = Ω·cmil/ft × 0.001662426112525

or Ω·mm²/m = Ω·cmil/ft ÷ 601.5304935757

Derivation from SI units:

• 1 Ω·cmil/ft = (π/4 × (25.4 µm)²) ÷ 0.3048 m Ω ≈ 1.6624 × 10⁻⁹ Ω·m; a circular mil is the area of a 1-mil-diameter circle
• 1 Ω·mm²/m = 10⁻⁶ Ω·m (resistance in Ω of a 1 m wire with 1 mm² cross-section)
• 1 Ω·cmil/ft = 1.662426112525 × 10⁻⁹ Ω·m ÷ 0.000001 Ω·m per Ω·mm²/m = 0.001662426112525 Ω·mm²/m

Both units are defined exactly, so the factor is exact. Ohm Circular Mil per Foot definition: ohm circular mil per foot; Ohm Square Millimetre per Metre definition: ohm square millimetre per metre.

Worked examples

1. A reading of 16.8 Ω·cmil/ft converts to 0.02792875869 Ω·mm²/m.
   16.8 Ω·cmil/ft × 0.001662426113 = 0.02792875869 Ω·mm²/m
2. A value of 100 Ω·cmil/ft is 0.1662426113 Ω·mm²/m.
   100 Ω·cmil/ft × 0.001662426113 = 0.1662426113 Ω·mm²/m

Where it's used

Ohm Circular Mils per Foot are used for US wire tables and AWG calculations, while ohm square millimetres per metre appear in cable and wire resistance (R = ρ × length ÷ mm²). Both measure electrical resistivity, so the conversion is a fixed factor.

Ohm Circular Mil per Foot to other electrical resistivity units

Frequently asked questions

Sources

• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "circular mil".
• Copper Wire Tables, NBS Handbook 100 (International Annealed Copper Standard), National Bureau of Standards (now NIST) .
• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .

Last reviewed: 2026-10-15. Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.