Convert Circular Mils to Square Millimeters
Convert Circular Mils (cmil) to Square Millimeters (mm²) instantly and accurately.
Conversion Formula
mm² = cmil × 0.0005067074791
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.
About Square Millimeters
A square millimeter (mm²) is a metric unit of area equal to a square with sides of one millimeter. It is commonly used in precision engineering, electronics, and measuring very small surfaces such as microchips or printed circuit boards. To visualise: a typical pinhead has an area of about 2-3 mm². This unit is essential in microscopy, medical imaging, and manufacturing where tiny, precise measurements are critical.
Quick Reference Table
| Circular Mils (cmil) | Square Millimeters (mm²) |
|---|---|
| 1 cmil | 0.000506707 mm² |
| 2 cmil | 0.00101341 mm² |
| 5 cmil | 0.00253354 mm² |
| 10 cmil | 0.00506707 mm² |
| 25 cmil | 0.0126677 mm² |
| 50 cmil | 0.0253354 mm² |
| 100 cmil | 0.0506707 mm² |