Convert Square Inches to Circular Mils

Convert Square Inches (in²) to Circular Mils (cmil) instantly and accurately.

Conversion Formula

cmil = in² × 1273239.545

About Square Inches

A square inch (in²) is an imperial unit of area equal to a square with sides of one inch (25.4 mm × 25.4 mm). It is commonly used in the United States for measuring small areas like fabric swatches, screen sizes, or printed materials. A standard business card is about 6 in², and a typical smartphone screen might be 15-20 in². This unit remains prevalent in American manufacturing, printing, and retail.

About Circular Mils

A circular mil (cmil) is a unit used in electrical engineering to specify the cross-sectional area of round wires and cables. Equal to the area of a circle with a diameter of exactly one thou (one thousandth of an inch) - approximately 5.067 × 10⁻¹⁰ m² - it simplifies wire calculations: the cross-sectional area in cmil equals the wire diameter in mils, squared. US electrical codes (NEC/NEMA) specify conductor sizes in circular mils, and large cables are rated in thousands of circular mils (kcmil or MCM). A 12 AWG wire, common in US household wiring, has a cross-section of 6,530 cmil.

Quick Reference Table

→ Full Area Converter