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 Hectometer [hm²]
A square hectometer (hm²) is a unit of area equal to a square with sides 1 hectometer (100 meters) long.
1 hm² = 10,000 m² = 1 hectare (ha).
It is used to measure large areas like fields or forests, similar to hectares.