Convert Circular Mil (circ mil) to Square Chain (ch²) instantly.
About these 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.
Square Chain (ch²)
A square chain equals the area of a square one chain (~66 feet) per side, resulting in 4,356 square feet, or exactly 1/10 of an acre. This unit is closely linked to the chain, a surveyor's unit standardized by Edmund Gunter in the 17th century. Because 10 square chains make an acre, survey calculations for early colonial and American lands were extremely efficient. Square chains allowed surveyors to map and divide land rapidly using ropes or metal chains, producing a legacy seen in long, straight property lines still visible today across rural landscapes.