Cable Size Calculator
Get an indicative minimum cable size for a circuit. Enter the load current, cable run length and supply type. This is a planning guide only, a licensed electrician must size the cable to the standard for your exact install.
How we estimate this
Cable size depends on the load current (how many amps the circuit carries) and the run length (longer runs need a bigger cable to limit voltage drop). This tool gives a rough starting point based on both.
Pricing reviewed: October 2026.
Doing more than just cable size?
Build a combined estimate across every part of your project in one place.
Pricing reviewed October 2026. Indicative Australian costs, not a quote.
Understanding cable sizes in Australia
Cable size depends on the load current (how many amps the circuit carries) and the run length (longer runs need a bigger cable to limit voltage drop). This tool gives a rough starting point based on both.
Real cable sizing to AS/NZS 3008 also accounts for the installation method, how cables are grouped, insulation type, ambient temperature and voltage-drop limits, which is why a licensed electrician must do the actual calculation.
Frequently asked questions
What size cable do I need?
It depends on the current and run length. As a rough guide, a 20A circuit often uses 2.5mm² and a 32A circuit 6mm², but longer runs need a bigger cable. A licensed electrician must confirm the size.
Can I size my own electrical cable?
You can estimate for planning, but in Australia the actual sizing and the wiring must be done by a licensed electrician to AS/NZS 3008 and the wiring rules.
Are you a electrician?
Everyone on this page is working out what cable size costs because they are ready to hire. Put your business right beneath the calculator, in your state, so you are who they find. From $50/mo.