- a unit used principally for measuring the cross-sectional area of wires, being the area of a circle having a diameter of one mil.
- a unit of area of cross section of wire, equal to the area of a circle whose diameter is one thousandth of an inch. 1 circular mil is equal to 0.785 × 10 –6 square inch or 0.2 × 10 –9 square metre
