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Cable sizing

Cable selection - Important notes

Factors for cable selection

  • Current: Maximum current that will flow through the cable
  • Ambient temperature: Higher temperatures reduce load capacity
  • Installation method: Affects heat dissipation (flush-mounted, cable duct, etc.)
  • Cable length: Longer cables have higher voltage drops

Safety margin

Always choose a cable cross-section with at least 20% reserve above the calculated load to allow for future expansions and avoid overloads.

Consider voltage drop

The voltage drop should not exceed the following values:

  • Lighting: max. 3% voltage drop
  • Motors and devices: max. 5% voltage drop
  • Long cables: For lengths over 50 m, pay special attention to voltage drop

Compliant installation

Always observe applicable standards (VDE 0100, DIN 18015) and have electrical installations carried out by professionals. The calculator is for guidance only.

Select network type

This setting is used for all calculations

Power & current

Calculate power

Calculate current

Cable cross-section & current carrying capacity

How to determine the right cable cross-section:

  1. Collect basic data: Enter your network type (taken from the selection above), current, cable length and the maximum permissible voltage drop.
  2. Double check: The calculator determines the cable cross-section based on two criteria:
    • By voltage drop, which considers the electrical performance over the cable length
    • By current carrying capacity, which considers the maximum load on the cable without overheating
  3. Recommendation: The higher of the two values is displayed as the recommended cable cross-section. This ensures sufficiently low voltage losses and safety against overheating.
Important: A cross-section that is too small can lead to heating, energy losses and, in the worst case, cable fires!

Calculate cable cross-section

Note on selection

The calculator takes into account both voltage drop and current carrying capacity and chooses the greater of the two values as the recommended cable cross-section.

Current carrying capacity for single-phase AC

Cross-section (mm²) Current carrying capacity (A)

* Values apply to copper conductors at 30°C ambient temperature

* Installation: B1 (in electrical installation conduit on or in the wall)

Current carrying capacity for three-phase (3 phases)

Cross-section (mm²) Current carrying capacity (A)

* Values apply to copper conductors at 30°C ambient temperature

* Installation: B2 (multi-core cable in electrical installation conduit)

Additional notes on cable selection

Installation method & ambient temperature

The values given in the tables apply to standardized installation methods. Depending on the specific installation, correction factors may be necessary:

  • High ambient temperatures (>30°C): Reduce capacity
  • Cable grouping: Reduce by 10–30% depending on the number of parallel cables
  • Insulated walls: Reduce by up to 50%

Special applications

  • Motor cables: Consider starting currents (approx. 5–7 times the nominal current)
  • Outdoor use: Use UV-resistant and weatherproof cables
  • Flush-mounted installation: At least 1.5 mm² for lighting and 2.5 mm² for sockets
  • Direct burial: Use special underground cables (NYY) with mechanical protection

Important: In case of doubt, always consult a qualified electrician!