Skip to content
AmpSize

Minimum conductor size lookup

Look up the smallest conductor allowed for a circuit.

AS/NZS 3000

Reads AS/NZS 3000:2018. Tables checked 26 Sept 2026.

Try a job 5

Each job fills in example values. Replace them with your values.

Inputs

Worked example with the default inputs. The live calculator replaces it when the page loads.

Use of the circuit
Socket-outlets
Conductor material
Copper
Conductors connected in parallel
No

Minimum conductor size

2.5mm²

Table 3.3 value
2.5mm²
Governed by
AS/NZS 3000:2018 Table 3.3

This result is a design aid. Verify it against the current standard.

Calculation steps

  1. Table 3.3 minimum size2.5mm²

    AS/NZS 3000:2018 Table 3.3

  2. Minimum size that appliesResult2.5mm²

    AS/NZS 3000:2018 Table 3.3

About this calculator

How this is calculated

The tool looks up the smallest conductor that AS/NZS 3000:2018 Table 3.3 allows for a use. It is a table lookup. It does not size a cable for current or voltage drop.

  1. Use. You pick the use: socket-outlets, other circuits, signal and relay control, bare conductors, insulated flexible conductors or aerial wiring.
  2. Material. You pick copper or aluminium. Table 3.3 has no aluminium row for some uses. The tool then refuses and says so.
  3. Table value. The tool reads the minimum cross-sectional area from Table 3.3 for that use and material.
  4. Parallel conductors. You can mark the conductors as run in parallel. The tool then compares the table value with the parallel floor and keeps the larger.
  5. Size that applies. The tool gives the minimum size that applies, and names Table 3.3 as the source.
StepTable or clauseWhat it decides
Table valueAS/NZS 3000 Table 3.3The smallest area for the use and material
Parallel floorCl 3.4.3The floor for a parallel group
Size that appliesTable 3.3The larger of the two

Worked example

Aerial wiring in copper. The tool gives 6 mm². The Table 3.3 value is also 6 mm², and the source is AS/NZS 3000:2018 Table 3.3.

Limits

  • Table 3.3 carries two exceptions. Read them before you use the size.
  • Exception 1 can allow a smaller socket-outlet conductor. It sets conditions that you must meet first.
  • The minimum is a floor. The cable must also pass current capacity, voltage drop and fault checks.
  • Use the cable size calculator for those checks.
  • Clause 3.4.3 sets more conditions on a parallel group than a minimum size.
  • The tool does not read AS/NZS 3008.1.

See also: Cable size calculator, Voltage drop calculator and What size breaker for 4 mm² cable.

Questions

Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.

What minimum cable size does a socket-outlet circuit need?

AS/NZS 3000:2018 Table 3.3 sets 2.5 square millimetres for a socket-outlet circuit. Exception 1 to the table can allow a smaller conductor, but only on the conditions it sets. Read Exception 1 in full before you go under the table value. The tool reports the table value and points at the exception.

What is the minimum size for a control or signal circuit?

Table 3.3 sets 1 square millimetre for other circuits and 0.5 square millimetres for relay control and signal circuits. Bare conductors are 6 square millimetres. Insulated flexible conductors are 0.75 square millimetres.

What size is needed for aerial wiring?

Table 3.3 sets 6 square millimetres for copper aerial wiring and 16 square millimetres for aluminium aerial wiring. Pick the material in the form to see the value that applies.

Does connecting cables in parallel change the minimum?

Yes. AS/NZS 3000:2018 Clause 3.4.3 puts a floor of 4 square millimetres under each cable in a parallel group. The clause sets further conditions as well. Read it in full before you design a parallel run.

Clauses and tables this tool reads

Every clause and table, with how each was verified

Tables last checked on 26 Sept 2026.

Related tools

Was this useful?

A question, or a value that looks wrong? Contact us.