Cable cross-sections – how to choose the right cable?
The cable cross-section (mm²) indicates how thick the copper or aluminum wire core is.
The larger the cross-section, the more electrical current the cable can safely carry.
Choosing the right cable is important for ensuring both the reliability of equipment and fire safety.
Why is cable cross-section important?
If the cable is too thin, it will overheat.
This can damage the insulation and, in the worst case, cause a short circuit or fire.
Too thick a cable means unnecessary expense, stiffness, and more complicated installation.
The cable cross-section must always correspond to:
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the power of the device (current in amperes),
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installation conditions (cable length, environment, temperature),
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permissible voltage drop.
Common cable cross-sections in home and industry
| Application | Recommended cut-off | Notes |
|---|---|---|
| Switches and lighting | 1.5 mm² | Suitable for lines with lower loads |
| Sockets | 2.5 mm² | A common choice in home installations |
| Air conditioner, water heater | 4.0 mm² | For more powerful consumers |
| House main cable | 6.0 mm² | Power cable from shield to distribution boards |
| Industrial use | 10 mm² and more | Heavy-duty equipment and machinery |
Good to know
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The cross-section of an electrical cable is expressed in mm² , not in the outer diameter of the wire.
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The material of the cable affects current conductivity — copper conducts electricity better than aluminum.
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Over longer distances, the voltage drop increases, requiring a cable with a larger cross-section.
Summary
When selecting a cable, the device's power, cable length, and installation conditions must be taken into account.
A simple rule of thumb:
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1.5 mm² – switches and lighting
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2.5 mm² – sockets
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4 mm² and more – more powerful devices and main cables
A properly selected cable ensures a safe and reliable electrical system — both at home and in industry.
