Convert Circular Inch (circ in) to Circular Mil (circ mil) instantly.
About these units
Circular Inch (circ in)
A circular inch represents the area of a circle with a diameter of exactly one inch. This yields an area of approximately 0.7854 square inches. It is sometimes used in engineering, especially in the sizing of pipes, hydraulic fittings, and certain mechanical components where circular cross-sections dominate. While not as widespread as the square inch, the circular inch offers a more direct representation of the actual shape of round components, reducing the need for manual geometric conversion.
Circular Mil (circ mil)
A circular mil is defined as the area of a circle with a diameter of exactly one mil. Because wires and cables have circular cross-sections, the circular mil has become a standard unit in electrical engineering for specifying conductor sizes. One circular mil simplifies calculations because area scales directly with the square of wire diameter without needing π in computations. For example, doubling a wire's diameter increases its circular-mil area fourfold. This makes circular mils extremely convenient for determining ampacity, resistance, and voltage drop in electrical conductors. Even though SI units are common elsewhere, the circular mil remains entrenched in North American electrical codes.