Convert Square Thou to Circular Mils
Convert Square Thou (thou²) to Circular Mils (cmil) instantly and accurately.
Conversion Formula
cmil = thou² × 1.273239545
About Square Thou
A square thou (thou²), sometimes called a square mil, is the area of a square with sides of one thousandth of an inch (0.0254 mm), equal to approximately 6.452 × 10⁻¹⁰ m². This tiny imperial unit is indispensable in precision engineering, PCB (printed circuit board) design, and manufacturing, where conductor widths, dielectric coating thicknesses, and tight machining tolerances are specified in thou. Wire insulation, thin films, and precision-stamped metal components are commonly described using this unit.
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
| Square Thou (thou²) | Circular Mils (cmil) |
|---|---|
| 1 thou² | 1.27324 cmil |
| 2 thou² | 2.54648 cmil |
| 5 thou² | 6.3662 cmil |
| 10 thou² | 12.7324 cmil |
| 25 thou² | 31.831 cmil |
| 50 thou² | 63.662 cmil |
| 100 thou² | 127.324 cmil |