Cable Sizing Calculator
AS/NZS 3008.1.1:2025 — Australian conditions
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AS/NZS 3000:2018 default limit is 5%
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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)
Cable Sizing Guide
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 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.