Cable Length Calculator Australia

Check the side flange of the drum — manufacturers stamp or print the empty tare weight directly on the timber or plastic reel. If the label is worn off, weigh an empty drum of the exact same size and brand from your workshop or wholesaler.

It is accurate within 5% to 10% on clean, undamaged cable drums. Moisture absorption on timber drums or heavy dirt build-up will add extra weight and slightly overestimate the length.

On a 230V single-phase circuit carrying 20A with a 5% maximum voltage drop limit (11.5V), 2.5mm² TPS copper reaches its limit at approximately 31 metres. For runs longer than 31 metres on a 20A breaker, step up to 4mm² TPS.

Standard domestic final sub-circuits should be run as continuous unbroken conductors wherever possible. If you must join cables, AS/NZS 3000 requires all junction boxes or crimp sleeves to remain accessible for inspection, unless using approved underground resin joint kits.

Short the active and neutral conductors together at the far end of the dead cable, then measure the total loop resistance from the near end using an ohm meter. Divide the measured ohms by twice the AS/NZS 3008 conductor resistance per metre to find the one-way route length.

Yes. Cable route length is the total physical length of conductor required from switchboard terminal to appliance terminal. Always add vertical wall drops, ceiling traverses, switchboard entry tails, and termination loops into your measurement.

AS/NZS 3000 Clause 3.6 limits overall voltage drop to 5% from the point of supply to any point in the installation. Many electricians design sub-mains for a maximum 1.5% to 2% drop to leave 3% to 3.5% head room for final sub-circuits.

Balanced three-phase systems divide the total load across three phase conductors, reducing line current per phase. Lower line current creates less voltage drop per metre, allowing a three-phase cable of the same mm² size to reach nearly double the distance of a single-phase run.

Add 10% to 15% on top of your measured building route. Switchboard wiring tails, wall cavity drops, bends around roof trusses, and stripping waste consume more cable than straight tape measurements show.

No. This calculator uses conductor mass and 50Hz AC impedance tables specifically for Australian building power cables (AS/NZS 3008). Data cables like Cat6 or RG6 coaxial have much thinner copper conductors and different sheath densities.

Conductor material (copper vs aluminium), conductor cross-section (mm²), number of cores, insulation compound (PVC vs XLPE), and outer sheath thickness all change the weight per metre. Always match your exact cable configuration in the calculator.

Use a portable platform scale or lug a digital hanging hook scale in your service ute. If you only have a bathroom scale, place a timber board across it, zero the scale, and roll the drum onto the board.

No. Aluminium has higher electrical resistivity than copper (about 1.65 times higher). An aluminium cable will hit the 5% voltage drop limit at roughly 60% of the distance of an equivalent mm² copper cable.

At 50 metres carrying 20A single-phase, 2.5mm² TPS drops 18.1V (7.8%), which fails AS/NZS 3000. You need 4mm² TPS minimum, which limits voltage drop to 11.3V (4.9%) over 50 metres.

The calculator uses standard AS/NZS 3008 reference values at 20°C ambient. If cables operate at elevated conductor temperatures (e.g. 75°C under continuous full load), conductor resistance increases by about 20%, which shortens the maximum compliant run length slightly.