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Cable Sizing Calculator

AS/NZS 3008.1.1:2025 (Australian conditions)

✓ 2025 Standard🔌 Phase 1 Calculator

Inputs

▶Advanced options

AS/NZS 3000:2018 default limit is 5%

Results

Recommended Cable Size

2.5

mm² copper

Earth: 2.5 mm²

✅

Current Carrying Capacity

23 A (>= 20 A)

✅

Voltage Drop

4.6 % (<= 5 %)

✅

Protection Device ≤ Cable Capacity

20 A (<= 23 A)

Combined Derating Factor1
Derated Current Capacity23 A
Actual Voltage Drop10.64 V (4.6%)
Important: These results are indicative only. Cable sizing tables are pending CPEng validation against AS/NZS 3008.1.1:2025. Do not use for final design without independent verification.

Cable Sizing Guide — AS/NZS 3008.1.1:2025

Cable sizing in Australia is governed by AS/NZS 3008.1.1:2025 (Australian conditions) and AS/NZS 3000:2018 (Wiring Rules). The 2025 edition of AS/NZS 3008.1.1 was published in December 2025 and introduces updated current rating tables, revised derating factors, and expanded coverage for modern installation methods including solar PV DC circuits.

The Three Checks Every Cable Must Pass

  • Current carrying capacity: The cable must carry the full load current continuously without exceeding its rated temperature.
  • Voltage drop: The voltage drop from source to load must not exceed 5% of the nominal supply voltage (AS/NZS 3000 Clause 3.6).
  • Earth fault loop impedance: The total earth fault loop impedance must be low enough to ensure the protection device disconnects within the required time.

Disclaimer: This calculator is provided as a guide only and must be verified by a qualified electrical engineer before use in design or installation. Always refer to the current edition of AS/NZS 3008.1.1 and AS/NZS 3000.