In general, for conductors such as ground wires or braided wires, which can be expressed as a single wire, the circular diameter of the wire can be used to describe its thickness. In some cables, if the conductors inside the cores consist of a single wire, then the thickness can also be expressed only by diameter.

The cross-section is defined as the surface area obtained when a conductor is cut perpendicular to its length, expressed in square millimeters (mm²).

For example, let us calculate the cross-sectional area of a wire with a diameter of Ø = 0.8 mm:

The radius of the wire is .

Since the cross-section is circular, the area is calculated using the circle area formula:

Therefore, a wire with a diameter of 0.8 mm has a cross-sectional area of 0.5 mm².

The cores inside a cable may consist of one or more wires. In this case, the core cross-section is expressed as the total cross-sectional area of all the wires inside the core.