Convert Square Millimeter (mm²) to Circular Mil (circ mil) instantly.
About these units
Square Millimeter (mm²)
A square millimeter represents the area of a square measuring 1 millimeter on each side. It is a tiny unit used extensively in engineering, electronics, material science, and medical instrumentation. Mechanical designers use mm² to determine cross-sectional areas of wires, beams, micro-mechanical parts, and precision components. In electronics, PCB traces, microchips, and sensors often specify dimensions in mm² for clarity and precision. Biomedical sciences also use mm² for cell colony measurements, tissue sample surfaces, and microscopic fields of view. Its size makes it ideal for quantifying structures too small for cm² but too large for micrometer-scale units.
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.