Cable Size Calculator Australia

Calculate the correct cable size (mm²) for circuits in Australia. Enter load, cable type, and installation method. Get current capacity and voltage drop. Based on AS/NZS 3008. Informational only—consult a qualified electrician.

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Published: October 23, 2025 | Updated: October 23, 2025 | Reviewed by: Science/Engineering Editor

⚠️ Electrical Safety Warning: This calculator is for informational purposes only. All electrical work must be performed by a licensed electrician and comply with AS/NZS 3008 and local regulations.

Circuit Parameters

Circuit load

Preset Circuits

AS/NZS 3008 Reference

This calculator uses simplified tables based on AS/NZS 3008.1.1. Always verify with the official standard and local regulations.

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How it works

We find the smallest cable size that meets both the current carrying capacity (from AS/NZS 3008 tables) and the voltage drop criteria. The calculation is Vd = (2 × I × L × R) / 1000.

The calculator considers cable type (copper/aluminium, single/multi-core), installation method, and circuit length to determine the appropriate cross-sectional area in mm².

Inputs explained

  • Load: The electrical load in kW or Amps
  • Cable Type: Material (copper/aluminium) and configuration (single/multi-core)
  • Installation Method: How the cable is installed affects heat dissipation
  • Circuit Length: Total cable run distance in meters
  • Phase: Single-phase (230V) or three-phase (400V)
  • Voltage Drop: Maximum acceptable voltage drop (typically 3-5%)

Example

Scenario: 5kW load, 3-phase, Copper cable, Enclosed in Conduit, 50m, 3% V-Drop

  • Load: 5 kW
  • Current: ~9 A (three-phase, 400V, PF=0.8)
  • Installation: Enclosed in Conduit
  • Recommended Size: 2.5mm² or 4mm²
  • Current Capacity: ~20-25 A
  • Voltage Drop: < 3%

Tips & notes

  • Undersized cables can overheat and pose a fire hazard
  • Voltage drop affects appliance performance and efficiency
  • Always consult AS/NZS 3008 and local electrical codes
  • Consider future load increases when sizing cables
  • Installation method significantly affects current capacity
  • Only licensed electricians should perform electrical work

FAQs

Based on the load, cable type, and installation method, using AS/NZS 3008 tables for current capacity and resistance.

AS/NZS 3008 is the standard for electrical installations in Australia and New Zealand.

Typically 3% for lighting circuits and 5% for power circuits, though stricter limits may apply in some situations.

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Disclaimer

Informational tool based on AS/NZS 3008. Electrical work must be done by a licensed professional and comply with local regulations. Consult a qualified electrician for all electrical installations.

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