# CM - Circular Mil Area

## The circular mil area - CM - is a unit denoting the cross-sectional size of a wire or cable

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The circular mil is a unit of area used especially when denoting the cross-sectional size of a wire or cable.

- A circular mil is the equivalent area of a circle whose diameter is
*0.001 (10*, or approximately^{-3}) inch*0.7854 millionths of a square inch*.

Mils of circular wire or cable can be calculated as:

mils = 1000 d (1)

where

d = diameter of cable or wire (inches)

#### Example - Calculating Mil

Mils of a *1 inch* wire:

mils = 1000 (1 in)

= 1000

Mils of a *1/2 inch* wire:

mils = 1000 (1/2 in)

= 500

### The Circular Mil

The circular mil area of a wire or cable is equal to its diameter - expressed in mils squared:

CM = mil^{2}(2)

where

CM = circular mil area (CM)

The diameter in mil of a circular wire can be expressed as:

mil = CM^{1/2}(2b)

#### Example - Calculating mil area

The mil area of an *3/8 in* wire* (0.375 in or 375 mil) *can be calculated as

CM= (375 mils) (375 mils)

= 140625 cmil

#### Example - Calculating mil

The mil of an circular wire with area *140625 CM* can be calculated as

mil =140625^{1/2}

= 375 mils

### The Square Mil Area

The square mil is the area of a square whose sides are one mil, or *1 x 10 ^{-3} inch*, and can be expressed as:

One Square Mil = (1 x 10^{-3})^{2}

= 1 x 10^{-6}in^{2}

### Converting Circular Mil to Square Inch

*1 Circular mil = 0.7854 x 10*^{-6}Square Inch

### Converting Circular Mil to Square Mil

*1 Circular Mil = 0.7854 Square Mil**1 Square Mil = 1.27 Circular Mils*

### Converting Circular Mil to metric units

*1 circular mil = 5.066 x 10*^{-10}m^{2}= 5.066 x 10^{-6}cm^{2}*1 m*^{2}= 1.974 x 10^{9}circular mil*1 cm*^{2}= 1.974 x 10^{5}circular mil

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