A circular mil (often abbreviated as cmil or kcmil) is a unit of area used primarily in the United States for measuring the cross-sectional area of a round wire or cable. It is a convenient unit for specifying the size of electrical conductors.
One circular mil is equal to the area of a circle with a diameter of one mil (1/1000th of an inch) or approximately 0.000000506707 square inches (in²). In metric units, one circular mil is approximately equal to 0.000001273 square millimeters (mm²).
Circular mils are commonly used in the American Wire Gauge (AWG) system to specify wire sizes. The AWG system assigns a unique number to each wire size, and this number is related to the wire's cross-sectional area in circular mils. For example, a larger AWG number corresponds to a smaller wire size with fewer circular mils, while a smaller AWG number corresponds to a larger wire size with more circular mils. This system allows for easy reference and selection of wire sizes for various electrical applications.
A square mile (often abbreviated as sq mi or mi²) is a unit of area used primarily in the United States and a few other countries. It is defined as the area of a square with sides that each measure one mile in length. One square mile is equal to 640 acres.
In terms of the International System of Units (SI), one square mile is approximately equal to 2.58999 square kilometers (km²).
To provide some perspective, a square mile is commonly used to describe land areas within cities, counties, and states in the United States. It's a convenient unit for measuring larger land areas, such as the size of cities or counties.