A 4 mm² cable is a medium‑sized electrical conductor commonly used in residential, commercial, and light industrial installations. The designation “4 mm²” refers to the cross‑sectional area of the conductor, which is four square millimetres. This size provides a balance between current‑carrying capacity, mechanical strength, and flexibility, making it suitable for circuits that require more power than small lighting lines but less than heavy industrial feeders.Typically, a 4 mm² cable is manufactured using copper conductors due to copper’s high electrical conductivity, good mechanical properties, and long‑term reliability. In some applications, aluminium conductors may be used, but copper remains more common in this size range. The conductor can be classed as solid or stranded. Solid conductors are used where the cable will remain fixed, while stranded conductors, made from multiple fine wires twisted together, provide better flexibility for routes involving bends or vibrations.Insulation materials for 4 mm² cables vary depending on the installation environment and regulatory standards. Common insulation types include PVC (polyvinyl chloride), XLPE (cross‑linked polyethylene), and rubber‑based compounds. PVC‑insulated cables are popular in general‑purpose indoor wiring because they are cost‑effective and easy to install. XLPE insulation offers improved thermal performance, higher temperature ratings, and better resistance to chemicals and moisture. For harsh or outdoor environments, additional sheathing or armouring may be applied to provide mechanical protection and resistance to abrasion, sunlight, and weather.In typical electrical systems, a 4 mm² cable is often used for power circuits supplying sockets with higher loads, air‑conditioning units, water heaters, small distribution boards, and certain kitchen equipment. It is also used for short feeder lines and sub‑circuits where voltage drop must be kept within acceptable limits. The permissible current‑carrying capacity depends on the installation method, ambient temperature, insulation type, and applicable standards, but it generally allows the safe supply of moderate power loads over reasonable distances.Compliance with national and international standards is essential. Standards specify conductor construction, insulation thickness, colour identification, test methods, and performance requirements such as dielectric strength and flame resistance. Proper selection of 4 mm² cable involves considering the rated voltage, frequency, environmental conditions, required current, and protection devices. Correct installation practices—such as using appropriate conduits, trunking, terminations, and over‑current protection—are necessary to ensure safety and long service life.Overall, 4 mm² cable is a versatile and widely used size in electrical engineering, offering a reliable solution for many medium‑duty power distribution applications in buildings and small‑scale infrastructure.