Circular Mil
A circular mil is a unit of area used mainly to measure the cross-sectional area of round wires and cables in electrical engineering.
Defined as the area of a circle with a diameter of 1 mil (1 mil = 0.001 inch).
Area = (diameter in mils)² circular mils.
1 circular mil ≈ 7.854 × 10⁻¹⁰ square meters or 0.7854 square mils.
Circular mils simplify calculations for round wires since area scales with the square of the diameter.
Square Millimeter [mm²]
A square millimeter (mm²) is a unit of area equal to a square with sides 1 millimeter long. It is used to measure very small surfaces, such as parts of mechanical components or electronic circuits.
1 mm² = 0.000001 m².